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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"status": "affected",
"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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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
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.
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- 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.