CVE-2026-82754 (GCVE-0-2026-82754)

Vulnerability from cvelistv5 – Published: 2026-09-07 22:23 – Updated: 2026-09-08 14:41
VLAI
Title
ash_authentication_oauth2_server aliases every protocol endpoint under /.well-known, bypassing path-scoped controls
Summary
Improper Protection of Alternate Path vulnerability in ash-project ash_authentication_oauth2_server exposes the state-changing OAuth endpoints under an unintended URL prefix, bypassing controls scoped to the canonical prefix. oauth2_server_protocol_routes/1 in AshAuthentication.Phoenix.Oauth2Server.Router forwards the same ProtocolRouter at both the /oauth prefix and the /.well-known prefix. Phoenix forward strips the matched prefix before dispatch, so the full route table answers under both mounts, and POST /register, POST /token, and POST /revoke are reachable as /.well-known/register, /.well-known/token, and /.well-known/revoke. Edge controls such as WAF rules, rate limits, or authentication exemptions written against the /oauth paths, or that allow-list /.well-known as unauthenticated, do not apply to the alias. This issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1.
Severity
6.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-08 14:41 UTC
CWE
  • CWE-424 - Improper Protection of Alternate Path
Assigner
EEF CNA under the mitre root
CNA scorecard A 97/100 over 357 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
ash-project ash_authentication_oauth2_server Affected: 0.1.0 , < 0.3.1 (semver)
    cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*
Create a notification for this product.
ash-project ash_authentication_oauth2_server Affected: 855b578037c5ded18e8a6e60f42e56bde4905fae , < a72972d7ed3eb74c05dfa0653a258ef14454459a (git)
    cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*
Create a notification for this product.
Credits
Peter Ullrich Peter Ullrich Zach Daniel / Ash Project Jonatan Männchen / EEF
Show details on NVD website
To clipboard 

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                "other": {
                  "content": {
                    "id": "CVE-2026-82754",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-09-08T14:41:33.862078Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-09-08T14:41:40.566Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "collectionURL": "https://repo.hex.pm",
              "cpes": [
                "cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*"
              ],
              "defaultStatus": "unaffected",
              "modules": [
                "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.Router\u0027",
                "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.ProtocolRouter\u0027"
              ],
              "packageName": "ash_authentication_oauth2_server",
              "packageURL": "pkg:hex/ash_authentication_oauth2_server",
              "product": "ash_authentication_oauth2_server",
              "programFiles": [
                "lib/ash_authentication_phoenix/oauth2_server/router.ex",
                "lib/ash_authentication_phoenix/oauth2_server/protocol_router.ex"
              ],
              "programRoutines": [
                {
                  "name": "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.Router\u0027:oauth2_server_protocol_routes/1"
                },
                {
                  "name": "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.ProtocolRouter\u0027:call/2"
                }
              ],
              "repo": "https://github.com/ash-project/ash_authentication_oauth2_server",
              "vendor": "ash-project",
              "versions": [
                {
                  "lessThan": "0.3.1",
                  "status": "affected",
                  "version": "0.1.0",
                  "versionType": "semver"
                }
              ]
            },
            {
              "collectionURL": "https://github.com",
              "cpes": [
                "cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*"
              ],
              "defaultStatus": "unaffected",
              "modules": [
                "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.Router\u0027",
                "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.ProtocolRouter\u0027"
              ],
              "packageName": "ash-project/ash_authentication_oauth2_server",
              "packageURL": "pkg:github/ash-project/ash_authentication_oauth2_server",
              "product": "ash_authentication_oauth2_server",
              "programFiles": [
                "lib/ash_authentication_phoenix/oauth2_server/router.ex",
                "lib/ash_authentication_phoenix/oauth2_server/protocol_router.ex"
              ],
              "programRoutines": [
                {
                  "name": "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.Router\u0027:oauth2_server_protocol_routes/1"
                },
                {
                  "name": "\u0027Elixir.AshAuthentication.Phoenix.Oauth2Server.ProtocolRouter\u0027:call/2"
                }
              ],
              "repo": "https://github.com/ash-project/ash_authentication_oauth2_server",
              "vendor": "ash-project",
              "versions": [
                {
                  "lessThan": "a72972d7ed3eb74c05dfa0653a258ef14454459a",
                  "status": "affected",
                  "version": "855b578037c5ded18e8a6e60f42e56bde4905fae",
                  "versionType": "git"
                }
              ]
            }
          ],
          "configurations": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "\u003cp\u003eThe routing alias is unconditional. Exploitable impact depends on the deployment applying path-scoped edge controls (WAF, rate limiting, auth-redirect exemptions) to the \u003ccode\u003e/oauth\u003c/code\u003e prefix, or allow-listing \u003ccode\u003e/.well-known\u003c/code\u003e as unauthenticated, that the alias then bypasses.\u003c/p\u003e"
                },
                {
                  "base64": false,
                  "type": "text/markdown",
                  "value": "The routing alias is unconditional. Exploitable impact depends on the deployment applying path-scoped edge controls (WAF, rate limiting, auth-redirect exemptions) to the `/oauth` prefix, or allow-listing `/.well-known` as unauthenticated, that the alias then bypasses."
                }
              ],
              "value": "The routing alias is unconditional. Exploitable impact depends on the deployment applying path-scoped edge controls (WAF, rate limiting, auth-redirect exemptions) to the /oauth prefix, or allow-listing /.well-known as unauthenticated, that the alias then bypasses."
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "0.3.1",
                      "versionStartIncluding": "0.1.0",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ],
              "operator": "AND"
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "finder",
              "value": "Peter Ullrich"
            },
            {
              "lang": "en",
              "type": "reporter",
              "value": "Peter Ullrich"
            },
            {
              "lang": "en",
              "type": "remediation developer",
              "value": "Zach Daniel / Ash Project"
            },
            {
              "lang": "en",
              "type": "coordinator",
              "value": "Jonatan M\u00e4nnchen / EEF"
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "\u003cp\u003eImproper Protection of Alternate Path vulnerability in ash-project ash_authentication_oauth2_server exposes the state-changing OAuth endpoints under an unintended URL prefix, bypassing controls scoped to the canonical prefix.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eoauth2_server_protocol_routes/1\u003c/code\u003e in \u003ccode\u003eAshAuthentication.Phoenix.Oauth2Server.Router\u003c/code\u003e forwards the same \u003ccode\u003eProtocolRouter\u003c/code\u003e at both the \u003ccode\u003e/oauth\u003c/code\u003e prefix and the \u003ccode\u003e/.well-known\u003c/code\u003e prefix. Phoenix \u003ccode\u003eforward\u003c/code\u003e strips the matched prefix before dispatch, so the full route table answers under both mounts, and \u003ccode\u003ePOST /register\u003c/code\u003e, \u003ccode\u003ePOST /token\u003c/code\u003e, and \u003ccode\u003ePOST /revoke\u003c/code\u003e are reachable as \u003ccode\u003e/.well-known/register\u003c/code\u003e, \u003ccode\u003e/.well-known/token\u003c/code\u003e, and \u003ccode\u003e/.well-known/revoke\u003c/code\u003e. Edge controls such as WAF rules, rate limits, or authentication exemptions written against the \u003ccode\u003e/oauth\u003c/code\u003e paths, or that allow-list \u003ccode\u003e/.well-known\u003c/code\u003e as unauthenticated, do not apply to the alias.\u003c/p\u003e\n\u003cp\u003eThis issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1.\u003c/p\u003e"
                },
                {
                  "base64": false,
                  "type": "text/markdown",
                  "value": "Improper Protection of Alternate Path vulnerability in ash-project ash_authentication_oauth2_server exposes the state-changing OAuth endpoints under an unintended URL prefix, bypassing controls scoped to the canonical prefix.\n\n`oauth2_server_protocol_routes/1` in `AshAuthentication.Phoenix.Oauth2Server.Router` forwards the same `ProtocolRouter` at both the `/oauth` prefix and the `/.well-known` prefix. Phoenix `forward` strips the matched prefix before dispatch, so the full route table answers under both mounts, and `POST /register`, `POST /token`, and `POST /revoke` are reachable as `/.well-known/register`, `/.well-known/token`, and `/.well-known/revoke`. Edge controls such as WAF rules, rate limits, or authentication exemptions written against the `/oauth` paths, or that allow-list `/.well-known` as unauthenticated, do not apply to the alias.\n\nThis issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1."
                }
              ],
              "value": "Improper Protection of Alternate Path vulnerability in ash-project ash_authentication_oauth2_server exposes the state-changing OAuth endpoints under an unintended URL prefix, bypassing controls scoped to the canonical prefix.\n\noauth2_server_protocol_routes/1 in AshAuthentication.Phoenix.Oauth2Server.Router forwards the same ProtocolRouter at both the /oauth prefix and the /.well-known prefix. Phoenix forward strips the matched prefix before dispatch, so the full route table answers under both mounts, and POST /register, POST /token, and POST /revoke are reachable as /.well-known/register, /.well-known/token, and /.well-known/revoke. Edge controls such as WAF rules, rate limits, or authentication exemptions written against the /oauth paths, or that allow-list /.well-known as unauthenticated, do not apply to the alias.\n\nThis issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1."
            }
          ],
          "impacts": [
            {
              "capecId": "CAPEC-554",
              "descriptions": [
                {
                  "lang": "en",
                  "value": "CAPEC-554 Functionality Bypass"
                }
              ]
            }
          ],
          "metrics": [
            {
              "cvssV4_0": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "PRESENT",
                "attackVector": "NETWORK",
                "baseScore": 6.3,
                "baseSeverity": "MEDIUM",
                "privilegesRequired": "NONE",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
                "version": "4.0",
                "vulnAvailabilityImpact": "NONE",
                "vulnConfidentialityImpact": "NONE",
                "vulnIntegrityImpact": "LOW",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-424",
                  "description": "CWE-424 Improper Protection of Alternate Path",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-09-07T22:23:56.762Z",
            "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "shortName": "EEF"
          },
          "references": [
            {
              "tags": [
                "vendor-advisory",
                "related"
              ],
              "url": "https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wwxg-h779-3wf4"
            },
            {
              "tags": [
                "related"
              ],
              "url": "https://cna.erlef.org/cves/CVE-2026-82754.html"
            },
            {
              "tags": [
                "related"
              ],
              "url": "https://osv.dev/vulnerability/EEF-CVE-2026-82754"
            },
            {
              "tags": [
                "patch"
              ],
              "url": "https://github.com/ash-project/ash_authentication_oauth2_server/commit/a72972d7ed3eb74c05dfa0653a258ef14454459a"
            }
          ],
          "source": {
            "discovery": "EXTERNAL"
          },
          "title": "ash_authentication_oauth2_server aliases every protocol endpoint under /.well-known, bypassing path-scoped controls"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "assignerShortName": "EEF",
        "cveId": "CVE-2026-82754",
        "datePublished": "2026-09-07T22:23:56.762Z",
        "dateReserved": "2026-08-31T01:00:10.817Z",
        "dateUpdated": "2026-09-07T22:23:56.762Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Sightings

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