Vulnerability-Lookup

CVE-2026-45045 (GCVE-0-2026-45045)

Vulnerability from cvelistv5 – Published: 2026-07-08 19:26 – Updated: 2026-07-09 13:20

Title

Fiber: X-Real-IP Spoofing via Header.Add() in BalancerForward

Summary

Fiber is an Express inspired web framework written in Go. Prior to 3.3.0 and 2.52.14, the BalancerForward proxy helper in middleware/proxy/proxy.go uses Header.Add() instead of Header.Set() when injecting X-Real-IP, allowing an attacker-supplied first X-Real-IP value to be forwarded to upstream servers for logging, rate limiting, and access control. This issue is fixed in version 3.3.0 and 2.52.14.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-09 13:19 UTC

CWE

CWE-290 - Authentication Bypass by Spoofing

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7673 records in the last 180 days details

References

7 references

URL	Tags
https://github.com/gofiber/fiber/security/advisor…	x_refsource_CONFIRM
https://github.com/gofiber/fiber/pull/4260	x_refsource_MISC
https://github.com/gofiber/fiber/pull/4495	x_refsource_MISC
https://github.com/gofiber/fiber/commit/1403cc829…	x_refsource_MISC
https://github.com/gofiber/fiber/commit/33c950128…	x_refsource_MISC
https://github.com/gofiber/fiber/releases/tag/v2.52.14	x_refsource_MISC
https://github.com/gofiber/fiber/releases/tag/v3.3.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
gofiber	fiber	Affected: >= 3.0.0-beta.2, < 3.3.0 Affected: < 2.52.14	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-45045

Vulnerability from fkie_nvd - Published: 2026-07-08 20:16 - Updated: 2026-07-15 20:50

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396	Patch
security-advisories@github.com	https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d	Patch
security-advisories@github.com	https://github.com/gofiber/fiber/pull/4260	Issue Tracking, Patch
security-advisories@github.com	https://github.com/gofiber/fiber/pull/4495	Issue Tracking, Patch
security-advisories@github.com	https://github.com/gofiber/fiber/releases/tag/v2.52.14	Release Notes
security-advisories@github.com	https://github.com/gofiber/fiber/releases/tag/v3.3.0	Release Notes
security-advisories@github.com	https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	gofiber	fiber	*
	gofiber	fiber	*

JSON

To clipboard

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        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-45045",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-09T13:19:42.395861Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-08T20:16:50.060",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Issue Tracking",
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/pull/4260"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Issue Tracking",
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/pull/4495"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/gofiber/fiber/releases/tag/v2.52.14"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/gofiber/fiber/releases/tag/v3.3.0"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-290"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-GCFQ-8GQF-4876

Vulnerability from github – Published: 2026-07-02 13:50 – Updated: 2026-08-04 21:52

Summary

GoFiber Vulnerable to X-Real-IP Spoofing via Header.Add() in BalancerForward

Details

Summary

The BalancerForward proxy helper in GoFiber uses Header.Add() instead of Header.Set() when injecting the X-Real-IP header. This appends the real client IP as a second header value rather than replacing any attacker-supplied value. Upstream servers that read the first X-Real-IP header (nginx, Express, most HTTP servers) use the attacker's spoofed IP for logging, rate limiting, and access control.

Vulnerable Code

File: middleware/proxy/proxy.go, lines 270-285

func BalancerForward(servers []string, clients ...*fasthttp.Client) fiber.Handler {
    r := &roundrobin{
        current: 0,
        pool:    servers,
    }
    return func(c fiber.Ctx) error {
        server := r.get()
        if !strings.HasPrefix(server, "http") {
            server = "http://" + server
        }
        c.Request().Header.Add("X-Real-IP", c.IP())   // line 282: Add, not Set
        return Do(c, server+c.OriginalURL(), clients...)
    }
}

Data Flow

Attacker sends request with X-Real-IP: 10.0.0.1 (spoofed internal IP)
BalancerForward handler executes at line 282
c.Request().Header.Add("X-Real-IP", c.IP()) APPENDS the real IP as a second header
Upstream server receives: X-Real-IP: 10.0.0.1 AND X-Real-IP: <real-attacker-ip>
Most HTTP servers (nginx, Node.js, Apache) read the FIRST value
Upstream uses 10.0.0.1 for all IP-dependent logic

Impact

Rate limit bypass: IP-based rate limiting at the upstream uses the spoofed IP, allowing unlimited requests
IP ACL bypass: Internal IP allowlists (e.g., admin panels restricted to 10.0.0.0/8) can be bypassed
Audit log poisoning: Security logs record the spoofed IP, making incident investigation unreliable
Geolocation bypass: IP-based geofencing or region restrictions are circumvented

Fix

Replace Header.Add() with Header.Set() at line 282:

c.Request().Header.Set("X-Real-IP", c.IP())

Header.Set() replaces any existing header value, ensuring only the real client IP is forwarded.

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.2.0"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/gofiber/fiber/v3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.52.13"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/gofiber/fiber/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.52.14"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45045"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-02T13:50:45Z",
    "nvd_published_at": "2026-07-08T20:16:50Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nThe `BalancerForward` proxy helper in GoFiber uses `Header.Add()` instead of `Header.Set()` when injecting the `X-Real-IP` header. This appends the real client IP as a second header value rather than replacing any attacker-supplied value. Upstream servers that read the first `X-Real-IP` header (nginx, Express, most HTTP servers) use the attacker\u0027s spoofed IP for logging, rate limiting, and access control.\n\n## Vulnerable Code\n\n**File:** `middleware/proxy/proxy.go`, lines 270-285\n\n```go\nfunc BalancerForward(servers []string, clients ...*fasthttp.Client) fiber.Handler {\n    r := \u0026roundrobin{\n        current: 0,\n        pool:    servers,\n    }\n    return func(c fiber.Ctx) error {\n        server := r.get()\n        if !strings.HasPrefix(server, \"http\") {\n            server = \"http://\" + server\n        }\n        c.Request().Header.Add(\"X-Real-IP\", c.IP())   // line 282: Add, not Set\n        return Do(c, server+c.OriginalURL(), clients...)\n    }\n}\n```\n\n## Data Flow\n\n1. Attacker sends request with `X-Real-IP: 10.0.0.1` (spoofed internal IP)\n2. `BalancerForward` handler executes at line 282\n3. `c.Request().Header.Add(\"X-Real-IP\", c.IP())` APPENDS the real IP as a second header\n4. Upstream server receives: `X-Real-IP: 10.0.0.1` AND `X-Real-IP: \u003creal-attacker-ip\u003e`\n5. Most HTTP servers (nginx, Node.js, Apache) read the FIRST value\n6. Upstream uses `10.0.0.1` for all IP-dependent logic\n\n## Impact\n\n- **Rate limit bypass:** IP-based rate limiting at the upstream uses the spoofed IP, allowing unlimited requests\n- **IP ACL bypass:** Internal IP allowlists (e.g., admin panels restricted to `10.0.0.0/8`) can be bypassed\n- **Audit log poisoning:** Security logs record the spoofed IP, making incident investigation unreliable\n- **Geolocation bypass:** IP-based geofencing or region restrictions are circumvented\n\n## Fix\n\nReplace `Header.Add()` with `Header.Set()` at line 282:\n\n```go\nc.Request().Header.Set(\"X-Real-IP\", c.IP())\n```\n\n`Header.Set()` replaces any existing header value, ensuring only the real client IP is forwarded.",
  "id": "GHSA-gcfq-8gqf-4876",
  "modified": "2026-08-04T21:52:02Z",
  "published": "2026-07-02T13:50:45Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45045"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/pull/4260"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/pull/4495"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/gofiber/fiber"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/releases/tag/v2.52.14"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/releases/tag/v3.3.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "GoFiber Vulnerable to X-Real-IP Spoofing via Header.Add() in BalancerForward"
}

Sightings

Author	Source	Type	Date	Other

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Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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CVE-2026-45045 (GCVE-0-2026-45045)

FKIE_CVE-2026-45045

GHSA-GCFQ-8GQF-4876

Summary

Vulnerable Code

Data Flow

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Fix

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