CVE-2026-66884 (GCVE-0-2026-66884)
Vulnerability from cvelistv5 – Published: 2026-08-04 11:45 – Updated: 2026-08-04 12:40
VLAI
EPSS
VEX
Title
Oidcc.Plug.AuthorizationCallback accepts callbacks with no authorize session or no state parameter, defeating CSRF protection
Summary
Cross-Site Request Forgery vulnerability in Erlang Ecosystem Foundation oidcc_plug (Oidcc.Plug.AuthorizationCallback module) allows an attacker to make a victim's browser complete an authorization flow the victim never initiated.
This vulnerability is associated with program file lib/oidcc/plug/authorization_callback.ex and program routine Oidcc.Plug.AuthorizationCallback.call/2.
A callback request that carries no Oidcc.Plug.Authorize session is processed with every security check disabled rather than being rejected. call/2 substitutes permissive defaults for the absent session, and each downstream check treats its value as nothing to compare and returns :ok, so the nonce, state, PKCE, peer IP and user agent checks are all skipped. A separate clause of check_state/2 also accepts a state-less request when a verifier is present.
An attacker obtains an authorization code for their own provider account, then induces the victim to visit the callback endpoint with that code and no state parameter. The application signs the victim in as the attacker, so the victim's subsequent actions occur in the attacker's account where the attacker can read them. Applications reusing one callback for both signing in and linking a provider account are further exposed to account takeover, the attacker's account becoming linked to the victim's.
The permissive fallback serves no conforming flow. Third-party-initiated login reaches a relying party at a separate login initiation endpoint and causes it to send a fresh authentication request, and this library implements no such endpoint. Oidcc.Plug.Authorize always sends a state parameter, which an authorization server must echo, so no legitimate callback lacks one.
This issue affects oidcc_plug: from 0.2.0-beta.1 before 0.5.0.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-352 - Cross-Site Request Forgery (CSRF)
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/erlef/oidcc_plug/security/advi… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-66884.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-66884 | related |
| https://github.com/erlef/oidcc_plug/commit/97d75a… | patch |
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| Erlang Ecosystem Foundation | oidcc_plug |
Affected:
0.2.0-beta.1 , < 0.5.0
(semver)
cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:* |
|
| Erlang Ecosystem Foundation | oidcc_plug |
Affected:
e577ae73b9080693442916043a22d8f05491dd93 , < 97d75afc57826dca31989b47d6e2a3c136039917
(git)
cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:* |
Credits
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"vulnrichment": {
"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-66884\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-04T12:37:09.321822Z\"}}}], \"references\": [{\"url\": \"https://github.com/erlef/oidcc_plug/security/advisories/GHSA-fg66-w5gp-22cr\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-04T12:40:37.053Z\"}}], \"cna\": {\"title\": \"Oidcc.Plug.AuthorizationCallback accepts callbacks with no authorize session or no state parameter, defeating CSRF protection\", \"source\": {\"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Mathias Polligkeit\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"Mathias Polligkeit\"}, {\"lang\": \"en\", \"type\": \"remediation reviewer\", \"value\": \"Jonatan M\\u00e4nnchen / EEF\"}, {\"lang\": \"en\", \"type\": \"coordinator\", \"value\": \"Jonatan M\\u00e4nnchen / EEF\"}], \"impacts\": [{\"capecId\": \"CAPEC-62\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"CAPEC-62 Cross Site Request Forgery\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 2.1, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"LOW\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"ACTIVE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"LOW\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"LOW\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:*\"], \"repo\": \"https://github.com/erlef/oidcc_plug\", \"vendor\": \"Erlang Ecosystem Foundation\", \"modules\": [\"Elixir.Oidcc.Plug.AuthorizationCallback\"], \"product\": \"oidcc_plug\", \"versions\": [{\"status\": \"affected\", \"version\": \"0.2.0-beta.1\", \"lessThan\": \"0.5.0\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:hex/oidcc_plug\", \"packageName\": \"oidcc_plug\", \"programFiles\": [\"lib/oidcc/plug/authorization_callback.ex\"], \"collectionURL\": \"https://repo.hex.pm\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.Oidcc.Plug.AuthorizationCallback\u0027:call/2\"}]}, {\"cpes\": [\"cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:*\"], \"repo\": \"https://github.com/erlef/oidcc_plug\", \"vendor\": \"Erlang Ecosystem Foundation\", \"modules\": [\"Elixir.Oidcc.Plug.AuthorizationCallback\"], \"product\": \"oidcc_plug\", \"versions\": [{\"status\": \"affected\", \"version\": \"e577ae73b9080693442916043a22d8f05491dd93\", \"lessThan\": \"97d75afc57826dca31989b47d6e2a3c136039917\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/erlef/oidcc_plug\", \"packageName\": \"erlef/oidcc_plug\", \"programFiles\": [\"lib/oidcc/plug/authorization_callback.ex\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.Oidcc.Plug.AuthorizationCallback\u0027:call/2\"}]}], \"references\": [{\"url\": \"https://github.com/erlef/oidcc_plug/security/advisories/GHSA-fg66-w5gp-22cr\", \"tags\": [\"vendor-advisory\", \"related\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-66884.html\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-66884\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/erlef/oidcc_plug/commit/97d75afc57826dca31989b47d6e2a3c136039917\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"Insert a plug before Oidcc.Plug.AuthorizationCallback that rejects the request when either the Oidcc.Plug.Authorize session or the state query parameter is missing. This restores the binding the callback fails to enforce and does not require modifying the library.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eInsert a plug before \u003ccode\u003eOidcc.Plug.AuthorizationCallback\u003c/code\u003e that rejects the request when either the \u003ccode\u003eOidcc.Plug.Authorize\u003c/code\u003e session or the \u003ccode\u003estate\u003c/code\u003e query parameter is missing. This restores the binding the callback fails to enforce and does not require modifying the library.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Insert a plug before `Oidcc.Plug.AuthorizationCallback` that rejects the request when either the `Oidcc.Plug.Authorize` session or the `state` query parameter is missing. This restores the binding the callback fails to enforce and does not require modifying the library.\", \"base64\": false}]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Cross-Site Request Forgery vulnerability in Erlang Ecosystem Foundation oidcc_plug (Oidcc.Plug.AuthorizationCallback module) allows an attacker to make a victim\u0027s browser complete an authorization flow the victim never initiated.\\n\\nThis vulnerability is associated with program file lib/oidcc/plug/authorization_callback.ex and program routine Oidcc.Plug.AuthorizationCallback.call/2.\\n\\nA callback request that carries no Oidcc.Plug.Authorize session is processed with every security check disabled rather than being rejected. call/2 substitutes permissive defaults for the absent session, and each downstream check treats its value as nothing to compare and returns :ok, so the nonce, state, PKCE, peer IP and user agent checks are all skipped. A separate clause of check_state/2 also accepts a state-less request when a verifier is present.\\n\\nAn attacker obtains an authorization code for their own provider account, then induces the victim to visit the callback endpoint with that code and no state parameter. The application signs the victim in as the attacker, so the victim\u0027s subsequent actions occur in the attacker\u0027s account where the attacker can read them. Applications reusing one callback for both signing in and linking a provider account are further exposed to account takeover, the attacker\u0027s account becoming linked to the victim\u0027s.\\n\\nThe permissive fallback serves no conforming flow. Third-party-initiated login reaches a relying party at a separate login initiation endpoint and causes it to send a fresh authentication request, and this library implements no such endpoint. Oidcc.Plug.Authorize always sends a state parameter, which an authorization server must echo, so no legitimate callback lacks one.\\n\\nThis issue affects oidcc_plug: from 0.2.0-beta.1 before 0.5.0.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eCross-Site Request Forgery vulnerability in Erlang Ecosystem Foundation oidcc_plug (\u003ccode\u003eOidcc.Plug.AuthorizationCallback\u003c/code\u003e module) allows an attacker to make a victim\u0027s browser complete an authorization flow the victim never initiated.\u003c/p\u003e\\n\u003cp\u003eThis vulnerability is associated with program file \u003ccode\u003elib/oidcc/plug/authorization_callback.ex\u003c/code\u003e and program routine \u003ccode\u003eOidcc.Plug.AuthorizationCallback.call/2\u003c/code\u003e.\u003c/p\u003e\\n\u003cp\u003eA callback request that carries no \u003ccode\u003eOidcc.Plug.Authorize\u003c/code\u003e session is processed with every security check disabled rather than being rejected. \u003ccode\u003ecall/2\u003c/code\u003e substitutes permissive defaults for the absent session, and each downstream check treats its value as nothing to compare and returns \u003ccode\u003e:ok\u003c/code\u003e, so the nonce, state, PKCE, peer IP and user agent checks are all skipped. A separate clause of \u003ccode\u003echeck_state/2\u003c/code\u003e also accepts a state-less request when a verifier is present.\u003c/p\u003e\\n\u003cp\u003eAn attacker obtains an authorization code for their own provider account, then induces the victim to visit the callback endpoint with that code and no \u003ccode\u003estate\u003c/code\u003e parameter. The application signs the victim in as the attacker, so the victim\u0027s subsequent actions occur in the attacker\u0027s account where the attacker can read them. Applications reusing one callback for both signing in and linking a provider account are further exposed to account takeover, the attacker\u0027s account becoming linked to the victim\u0027s.\u003c/p\u003e\\n\u003cp\u003eThe permissive fallback serves no conforming flow. Third-party-initiated login reaches a relying party at a separate login initiation endpoint and causes it to send a fresh authentication request, and this library implements no such endpoint. \u003ccode\u003eOidcc.Plug.Authorize\u003c/code\u003e always sends a \u003ccode\u003estate\u003c/code\u003e parameter, which an authorization server must echo, so no legitimate callback lacks one.\u003c/p\u003e\\n\u003cp\u003eThis issue affects oidcc_plug: from 0.2.0-beta.1 before 0.5.0.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Cross-Site Request Forgery vulnerability in Erlang Ecosystem Foundation oidcc_plug (`Oidcc.Plug.AuthorizationCallback` module) allows an attacker to make a victim\u0027s browser complete an authorization flow the victim never initiated.\\n\\nThis vulnerability is associated with program file `lib/oidcc/plug/authorization_callback.ex` and program routine `Oidcc.Plug.AuthorizationCallback.call/2`.\\n\\nA callback request that carries no `Oidcc.Plug.Authorize` session is processed with every security check disabled rather than being rejected. `call/2` substitutes permissive defaults for the absent session, and each downstream check treats its value as nothing to compare and returns `:ok`, so the nonce, state, PKCE, peer IP and user agent checks are all skipped. A separate clause of `check_state/2` also accepts a state-less request when a verifier is present.\\n\\nAn attacker obtains an authorization code for their own provider account, then induces the victim to visit the callback endpoint with that code and no `state` parameter. The application signs the victim in as the attacker, so the victim\u0027s subsequent actions occur in the attacker\u0027s account where the attacker can read them. Applications reusing one callback for both signing in and linking a provider account are further exposed to account takeover, the attacker\u0027s account becoming linked to the victim\u0027s.\\n\\nThe permissive fallback serves no conforming flow. Third-party-initiated login reaches a relying party at a separate login initiation endpoint and causes it to send a fresh authentication request, and this library implements no such endpoint. `Oidcc.Plug.Authorize` always sends a `state` parameter, which an authorization server must echo, so no legitimate callback lacks one.\\n\\nThis issue affects oidcc_plug: from 0.2.0-beta.1 before 0.5.0.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-352\", \"description\": \"CWE-352 Cross-Site Request Forgery (CSRF)\"}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:erlef:oidcc_plug:*:*:*:*:*:erlang:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"0.5.0\", \"versionStartIncluding\": \"0.2.0-beta.1\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-08-04T11:45:49.464Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-66884\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-04T12:40:41.232Z\", \"dateReserved\": \"2026-07-28T04:15:10.240Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-08-04T11:45:49.464Z\", \"assignerShortName\": \"EEF\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- 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.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- 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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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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