CVE-2026-81637 (GCVE-0-2026-81637)
Vulnerability from cvelistv5 – Published: 2026-09-17 13:09 – Updated: 2026-09-17 18:26
VLAI
EPSS
VEX
Title
Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication
Summary
Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 state value to replay the callback and sign that victim into an attacker-controlled account.
AshAuthentication.Strategy.OAuth2.Plug.callback/2 clears the stored session_params through a rebinding step inside its with chain, conn <- delete_session(conn, session_key). Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.
This issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-17 18:26 UTC
CWE
- CWE-613 - Insufficient Session Expiration
Assigner
References
6 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| team-alembic | ash_authentication |
Affected:
0.6.0 , < 4.15.0
(semver)
Affected: 5.0.0-rc.0 , < 5.0.0-rc.14 (semver) cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:* |
||
| team-alembic | ash_authentication |
Affected:
c5f589058e04239263f50a1430eb17ea6d5dd1a2 , < *
(git)
cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:* |
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"version": "0.6.0",
"versionType": "semver"
},
{
"lessThan": "5.0.0-rc.14",
"status": "affected",
"version": "5.0.0-rc.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.AshAuthentication.Strategy.OAuth2.Plug\u0027"
],
"packageName": "team-alembic/ash_authentication",
"packageURL": "pkg:github/team-alembic/ash_authentication",
"product": "ash_authentication",
"programFiles": [
"lib/ash_authentication/strategies/oauth2/plug.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.AshAuthentication.Strategy.OAuth2.Plug\u0027:callback/2"
},
{
"name": "\u0027Elixir.AshAuthentication.Strategy.OAuth2.Plug\u0027:request/2"
}
],
"repo": "https://github.com/team-alembic/ash_authentication",
"vendor": "team-alembic",
"versions": [
{
"changes": [
{
"at": "bd4352303bc9d72d007f6818775267585a4bcc2f",
"status": "unaffected"
},
{
"at": "d7f939cd02bd618bcaa304631846fa75ffc419d7",
"status": "unaffected"
}
],
"lessThan": "*",
"status": "affected",
"version": "c5f589058e04239263f50a1430eb17ea6d5dd1a2",
"versionType": "git"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.15.0",
"versionStartIncluding": "0.6.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.0.0-rc.14",
"versionStartIncluding": "5.0.0-rc.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "reporter",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
},
{
"lang": "en",
"type": "remediation developer",
"value": "James Harton"
}
],
"dateAssigned": "2026-09-11T18:16:32.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eInsufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim\u0027s OAuth2 \u003ccode\u003estate\u003c/code\u003e value to replay the callback and sign that victim into an attacker-controlled account.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eAshAuthentication.Strategy.OAuth2.Plug.callback/2\u003c/code\u003e clears the stored \u003ccode\u003esession_params\u003c/code\u003e through a rebinding step inside its \u003ccode\u003ewith\u003c/code\u003e chain, \u003ccode\u003econn \u0026lt;- delete_session(conn, session_key)\u003c/code\u003e. Elixir evaluates the \u003ccode\u003eelse\u003c/code\u003e block in the scope enclosing the \u003ccode\u003ewith\u003c/code\u003e, so every failure path (the provider returning \u003ccode\u003e?error=access_denied\u003c/code\u003e, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches \u003ccode\u003estore_authentication_result/2\u003c/code\u003e holding the original connection and the session entry is never removed. The value the module\u0027s own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\u003c/p\u003e\n\u003cp\u003eThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim\u0027s OAuth2 `state` value to replay the callback and sign that victim into an attacker-controlled account.\n\n`AshAuthentication.Strategy.OAuth2.Plug.callback/2` clears the stored `session_params` through a rebinding step inside its `with` chain, `conn \u003c- delete_session(conn, session_key)`. Elixir evaluates the `else` block in the scope enclosing the `with`, so every failure path (the provider returning `?error=access_denied`, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches `store_authentication_result/2` holding the original connection and the session entry is never removed. The value the module\u0027s own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\n\nThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14."
}
],
"value": "Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim\u0027s OAuth2 state value to replay the callback and sign that victim into an attacker-controlled account.\n\nAshAuthentication.Strategy.OAuth2.Plug.callback/2 clears the stored session_params through a rebinding step inside its with chain, conn \u003c- delete_session(conn, session_key). Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module\u0027s own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\n\nThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14."
}
],
"impacts": [
{
"capecId": "CAPEC-60",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-60 Reusing Session IDs (aka Session Replay)"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "HIGH",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 2.3,
"baseSeverity": "LOW",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "PASSIVE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-613",
"description": "CWE-613 Insufficient Session Expiration",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-17T13:09:06.571Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-3vcj-gxx8-3p44"
},
{
"name": "EEF CNA record for CVE-2026-81637",
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-81637.html"
},
{
"name": "OSV record EEF-CVE-2026-81637",
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-81637"
},
{
"name": "Introducing commit c5f5890 in team-alembic/ash_authentication",
"tags": [
"related"
],
"url": "https://github.com/team-alembic/ash_authentication/commit/c5f589058e04239263f50a1430eb17ea6d5dd1a2"
},
{
"name": "Fix commit bd43523 in team-alembic/ash_authentication",
"tags": [
"patch"
],
"url": "https://github.com/team-alembic/ash_authentication/commit/bd4352303bc9d72d007f6818775267585a4bcc2f"
},
{
"name": "Fix commit d7f939c in team-alembic/ash_authentication",
"tags": [
"patch"
],
"url": "https://github.com/team-alembic/ash_authentication/commit/d7f939cd02bd618bcaa304631846fa75ffc419d7"
}
],
"source": {
"discovery": "INTERNAL"
},
"title": "Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication"
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-81637",
"datePublished": "2026-09-17T13:09:06.571Z",
"dateReserved": "2026-09-11T18:15:01.808Z",
"dateUpdated": "2026-09-17T18:26:58.389Z",
"state": "PUBLISHED"
},
"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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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