FKIE_CVE-2026-66883

Vulnerability from fkie_nvd - Published: 2026-08-04 12:16 - Updated: 2026-08-04 14:52
Severity
6.3 (Medium) - CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Summary
Improper Handling of Case Sensitivity vulnerability in Erlang Ecosystem Foundation oidcc_plug (Oidcc.Plug.Authorize module) renders the user agent session binding inert, removing a defense in depth control against replay of a stolen session. This vulnerability is associated with program files lib/oidcc/plug/authorize.ex and lib/oidcc/plug/authorization_callback.ex, and program routines Oidcc.Plug.Authorize.call/2 and Oidcc.Plug.AuthorizationCallback.call/2. Oidcc.Plug.Authorize.call/2 reads the initiating client's user agent with get_req_header(conn, "User-Agent"). Plug lowercases incoming header names, but get_req_header/2 matches the supplied key exactly and performs no normalization of its own, so the mixed-case lookup always returns an empty list and nil is written into the session. On the callback side, Oidcc.Plug.AuthorizationCallback treats a stored nil user agent as nothing to compare and returns :ok without inspecting the request. The two behaviours combine so that the check passes unconditionally on every request, including for deployments that explicitly opted in with check_useragent: true, and an authorization callback can be completed from a different user agent than the one that initiated the flow without detection. The check fails open silently, with no error and no log entry, so a deployment cannot tell the binding is absent. The impact is limited to defense in depth. The inert check does not by itself allow an attacker to complete an authorization flow; it removes one layer that would otherwise hinder use of a stolen or leaked session, such as an exfiltrated session cookie replayed from a different client. The CSRF/state, nonce, and PKCE checks are unaffected and continue to function. Deployments that never enabled check_useragent are not affected in practice, since they never expected the binding. The corresponding lookup in Oidcc.Plug.AuthorizationCallback correctly uses the lowercase key and is not affected. This issue affects oidcc_plug: from 0.1.0-alpha.3 before 0.5.0.
References
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://cna.erlef.org/cves/CVE-2026-66883.html
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/erlef/oidcc_plug/commit/f15e52c5750aaba701104b10ed96cfac063bd557
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/erlef/oidcc_plug/security/advisories/GHSA-w5r8-m75h-98fc
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://osv.dev/vulnerability/EEF-CVE-2026-66883
134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/erlef/oidcc_plug/security/advisories/GHSA-w5r8-m75h-98fc
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "Elixir.Oidcc.Plug.Authorize",
            "Elixir.Oidcc.Plug.AuthorizationCallback"
          ],
          "packageName": "oidcc_plug",
          "packageURL": "pkg:hex/oidcc_plug",
          "product": "oidcc_plug",
          "programFiles": [
            "lib/oidcc/plug/authorize.ex",
            "lib/oidcc/plug/authorization_callback.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Oidcc.Plug.Authorize\u0027:call/2"
            },
            {
              "name": "\u0027Elixir.Oidcc.Plug.AuthorizationCallback\u0027:call/2"
            }
          ],
          "repo": "https://github.com/erlef/oidcc_plug",
          "vendor": "Erlang Ecosystem Foundation",
          "versions": [
            {
              "lessThan": "0.5.0",
              "status": "affected",
              "version": "0.1.0-alpha.3",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "Elixir.Oidcc.Plug.Authorize",
            "Elixir.Oidcc.Plug.AuthorizationCallback"
          ],
          "packageName": "erlef/oidcc_plug",
          "packageURL": "pkg:github/erlef/oidcc_plug",
          "product": "oidcc_plug",
          "programFiles": [
            "lib/oidcc/plug/authorize.ex",
            "lib/oidcc/plug/authorization_callback.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Oidcc.Plug.Authorize\u0027:call/2"
            },
            {
              "name": "\u0027Elixir.Oidcc.Plug.AuthorizationCallback\u0027:call/2"
            }
          ],
          "repo": "https://github.com/erlef/oidcc_plug",
          "vendor": "Erlang Ecosystem Foundation",
          "versions": [
            {
              "lessThan": "f15e52c5750aaba701104b10ed96cfac063bd557",
              "status": "affected",
              "version": "0a75fb139d8e2686d1b75e0d48962323d2181673",
              "versionType": "git"
            }
          ]
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Improper Handling of Case Sensitivity vulnerability in Erlang Ecosystem Foundation oidcc_plug (Oidcc.Plug.Authorize module) renders the user agent session binding inert, removing a defense in depth control against replay of a stolen session.\n\nThis vulnerability is associated with program files lib/oidcc/plug/authorize.ex and lib/oidcc/plug/authorization_callback.ex, and program routines Oidcc.Plug.Authorize.call/2 and Oidcc.Plug.AuthorizationCallback.call/2.\n\nOidcc.Plug.Authorize.call/2 reads the initiating client\u0027s user agent with get_req_header(conn, \"User-Agent\"). Plug lowercases incoming header names, but get_req_header/2 matches the supplied key exactly and performs no normalization of its own, so the mixed-case lookup always returns an empty list and nil is written into the session. On the callback side, Oidcc.Plug.AuthorizationCallback treats a stored nil user agent as nothing to compare and returns :ok without inspecting the request. The two behaviours combine so that the check passes unconditionally on every request, including for deployments that explicitly opted in with check_useragent: true, and an authorization callback can be completed from a different user agent than the one that initiated the flow without detection. The check fails open silently, with no error and no log entry, so a deployment cannot tell the binding is absent.\n\nThe impact is limited to defense in depth. The inert check does not by itself allow an attacker to complete an authorization flow; it removes one layer that would otherwise hinder use of a stolen or leaked session, such as an exfiltrated session cookie replayed from a different client. The CSRF/state, nonce, and PKCE checks are unaffected and continue to function. Deployments that never enabled check_useragent are not affected in practice, since they never expected the binding. The corresponding lookup in Oidcc.Plug.AuthorizationCallback correctly uses the lowercase key and is not affected.\n\nThis issue affects oidcc_plug: from 0.1.0-alpha.3 before 0.5.0."
    }
  ],
  "id": "CVE-2026-66883",
  "lastModified": "2026-08-04T14:52:54.493",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "HIGH",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-66883",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-04T12:27:16.535019Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-04T12:16:36.163",
  "references": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://cna.erlef.org/cves/CVE-2026-66883.html"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/erlef/oidcc_plug/commit/f15e52c5750aaba701104b10ed96cfac063bd557"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/erlef/oidcc_plug/security/advisories/GHSA-w5r8-m75h-98fc"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-66883"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/erlef/oidcc_plug/security/advisories/GHSA-w5r8-m75h-98fc"
    }
  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-178"
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
  ]
}



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