CVE-2026-82761 (GCVE-0-2026-82761)
Vulnerability from cvelistv5
Published
2026-09-17 13:09
Modified
2026-09-17 18:26
Severity ?
VLAI Severity ?
EPSS score ?
CWE
- CWE-367 - Time-of-check Time-of-use (TOCTOU) Race Condition
Summary
Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in team-alembic AshAuthentication allows an attacker holding a leaked magic link to replay its single-use token and authenticate as the target subject. A magic link configured with single_use_token?, which is the default, is meant to be redeemable exactly once, but nothing serialises the token's validity check against its consumption, so concurrent redemptions of one token all succeed and each yields a full user token.
Sign-in verifies the JWT with Jwt.verify/4 and revokes it only afterwards: AshAuthentication.Strategy.MagicLink.SignInPreparation revokes in a Query.after_action callback, and AshAuthentication.Strategy.MagicLink.SignInChange in an after_transaction hook that runs once the sign-in has already committed. AshAuthentication.TokenResource.Actions.revoke/3 writes the revocation as an upsert, so a concurrent duplicate revocation silently succeeds instead of conflicting and no request ever loses the race.
This issue affects ash_authentication: from 3.9.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| team-alembic | ash_authentication |
Version: 3.9.0 ≤ Version: 5.0.0-rc.0 ≤ cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:* |
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AshAuthentication.TokenResource.Actions.revoke/3 writes the revocation as an upsert, so a concurrent duplicate revocation silently succeeds instead of conflicting and no request ever loses the race.\\n\\nThis issue affects ash_authentication: from 3.9.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eTime-of-check Time-of-use (TOCTOU) Race Condition vulnerability in team-alembic AshAuthentication allows an attacker holding a leaked magic link to replay its single-use token and authenticate as the target subject. A magic link configured with \u003ccode\u003esingle_use_token?\u003c/code\u003e, which is the default, is meant to be redeemable exactly once, but nothing serialises the token\u0027s validity check against its consumption, so concurrent redemptions of one token all succeed and each yields a full user token.\u003c/p\u003e\\n\u003cp\u003eSign-in verifies the JWT with \u003ccode\u003eJwt.verify/4\u003c/code\u003e and revokes it only afterwards: \u003ccode\u003eAshAuthentication.Strategy.MagicLink.SignInPreparation\u003c/code\u003e revokes in a \u003ccode\u003eQuery.after_action\u003c/code\u003e callback, and \u003ccode\u003eAshAuthentication.Strategy.MagicLink.SignInChange\u003c/code\u003e in an \u003ccode\u003eafter_transaction\u003c/code\u003e hook that runs once the sign-in has already committed. \u003ccode\u003eAshAuthentication.TokenResource.Actions.revoke/3\u003c/code\u003e writes the revocation as an upsert, so a concurrent duplicate revocation silently succeeds instead of conflicting and no request ever loses the race.\u003c/p\u003e\\n\u003cp\u003eThis issue affects ash_authentication: from 3.9.0 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\": \"Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in team-alembic AshAuthentication allows an attacker holding a leaked magic link to replay its single-use token and authenticate as the target subject. A magic link configured with `single_use_token?`, which is the default, is meant to be redeemable exactly once, but nothing serialises the token\u0027s validity check against its consumption, so concurrent redemptions of one token all succeed and each yields a full user token.\\n\\nSign-in verifies the JWT with `Jwt.verify/4` and revokes it only afterwards: `AshAuthentication.Strategy.MagicLink.SignInPreparation` revokes in a `Query.after_action` callback, and `AshAuthentication.Strategy.MagicLink.SignInChange` in an `after_transaction` hook that runs once the sign-in has already committed. `AshAuthentication.TokenResource.Actions.revoke/3` writes the revocation as an upsert, so a concurrent duplicate revocation silently succeeds instead of conflicting and no request ever loses the race.\\n\\nThis issue affects ash_authentication: from 3.9.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-367\", \"description\": \"CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition\"}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.15.0\", \"versionStartIncluding\": \"3.9.0\"}, {\"criteria\": \"cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.0.0-rc.14\", \"versionStartIncluding\": \"5.0.0-rc.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-09-17T13:09:01.534Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-82761\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-17T18:26:08.563Z\", \"dateReserved\": \"2026-08-31T01:00:10.817Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-09-17T13:09:01.534Z\", \"assignerShortName\": \"EEF\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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