eef-cve-2026-82761
CVSS 9.1 osv_hex
Description
## 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.
Timeline
- Published
- unknown
- Last Modified
- unknown
CVSS Details
CVSS details not available.
Affected Products
No product information available.
Weaknesses (CWE)
References
- https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-23gr-vcp4-r27q
- https://cna.erlef.org/cves/CVE-2026-82761.html
- https://github.com/team-alembic/ash_authentication/commit/cf3d227ef25912cf1b0c5fa80f20001f5c46a102
- https://github.com/team-alembic/ash_authentication/commit/18dfdb36c14aa6a61df8572bce2d5ec36b1d9840
- https://github.com/team-alembic/ash_authentication/commit/9ef6864b8833d3b795427a7b8dc518a4997d41ab
- https://hex.pm/packages/ash_authentication
Linked Vulnerabilities
No linked vulnerabilities found.
{
"affected": [
{
"database_specific": {
"source": "https://cna.erlef.org/osv/EEF-CVE-2026-82761.json"
},
"package": {
"ecosystem": "Hex",
"name": "ash_authentication",
"purl": "pkg:hex/ash_authentication"
},
"ranges": [
{
"events": [
{
"introduced": "3.9.0"
},
{
"fixed": "4.15.0"
}
],
"type": "SEMVER"
},
{
"events": [
{
"introduced": "5.0.0-rc.0"
},
{
"fixed": "5.0.0-rc.14"
}
],
"type": "SEMVER"
}
],
"versions": [
"3.10.0",
"3.10.1",
"3.10.2",
"3.10.3",
"3.10.4",
"3.10.5",
"3.10.6",
"3.10.7",
"3.10.8",
"3.11.0",
"3.11.1",
"3.11.10",
"3.11.11",
"3.11.12",
"3.11.13",
"3.11.14",
"3.11.15",
"3.11.16",
"3.11.2",
"3.11.3",
"3.11.4",
"3.11.5",
"3.11.6",
"3.11.7",
"3.11.8",
"3.11.9",
"3.12.0",
"3.12.1",
"3.12.2",
"3.12.3",
"3.12.4",
"3.9.0",
"3.9.1",
"3.9.2",
"3.9.3",
"3.9.4",
"3.9.5",
"3.9.6",
"4.0.0",
"4.0.0-rc.0",
"4.0.0-rc.1",
"4.0.0-rc.2",
"4.0.0-rc.3",
"4.0.0-rc.5",
"4.0.0-rc.6",
"4.0.1",
"4.0.2",
"4.0.3",
"4.0.4",
"4.1.0",
"4.10.0",
"4.11.0",
"4.12.0",
"4.13.0",
"4.13.1",
"4.13.2",
"4.13.3",
"4.13.4",
"4.13.5",
"4.13.6",
"4.13.7",
"4.14.0",
"4.14.1",
"4.14.2",
"4.2.0",
"4.2.1",
"4.2.2",
"4.2.3",
"4.2.4",
"4.2.5",
"4.2.6",
"4.2.7",
"4.3.0",
"4.3.1",
"4.3.10",
"4.3.11",
"4.3.12",
"4.3.2",
"4.3.3",
"4.3.4",
"4.3.5",
"4.3.6",
"4.3.7",
"4.3.8",
"4.3.9",
"4.4.0",
"4.4.1",
"4.4.2",
"4.4.3",
"4.4.4",
"4.4.5",
"4.4.6",
"4.4.7",
"4.4.8",
"4.4.9",
"4.5.0",
"4.5.1",
"4.5.2",
"4.5.3",
"4.5.4",
"4.5.5",
"4.5.6",
"4.6.0",
"4.6.1",
"4.6.2",
"4.6.3",
"4.6.4",
"4.7.0",
"4.7.1",
"4.7.2",
"4.7.3",
"4.7.4",
"4.7.5",
"4.7.6",
"4.8.0",
"4.8.1",
"4.8.2",
"4.8.3",
"4.8.5",
"4.8.6",
"4.8.7",
"4.9.0",
"4.9.1",
"4.9.2",
"4.9.3",
"4.9.4",
"4.9.5",
"4.9.6",
"4.9.7",
"4.9.8",
"4.9.9",
"5.0.0-rc.0",
"5.0.0-rc.1",
"5.0.0-rc.10",
"5.0.0-rc.11",
"5.0.0-rc.12",
"5.0.0-rc.13",
"5.0.0-rc.2",
"5.0.0-rc.3",
"5.0.0-rc.4",
"5.0.0-rc.5",
"5.0.0-rc.6",
"5.0.0-rc.7",
"5.0.0-rc.8",
"5.0.0-rc.9"
]
},
{
"database_specific": {
"source": "https://cna.erlef.org/osv/EEF-CVE-2026-82761.json"
},
"ranges": [
{
"events": [
{
"introduced": "cf3d227ef25912cf1b0c5fa80f20001f5c46a102"
},
{
"fixed": "18dfdb36c14aa6a61df8572bce2d5ec36b1d9840"
},
{
"fixed": "9ef6864b8833d3b795427a7b8dc518a4997d41ab"
}
],
"repo": "https://github.com/team-alembic/ash_authentication",
"type": "GIT"
}
],
"versions": [
"v4.14.2",
"v5.0.0-rc.13",
"v4.14.1",
"v5.0.0-rc.12",
"v5.0.0-rc.11",
"v5.0.0-rc.10",
"v4.14.0",
"v4.13.7",
"5.0.0-rc.9",
"5.0.0-rc.8",
"v5.0.0-rc.7",
"v5.0.0-rc.6",
"v5.0.0-rc.5",
"v5.0.0-rc.4",
"v5.0.0-rc.3",
"v5.0.0-rc.2",
"v5.0.0-rc.1",
"v5.0.0-rc.0",
"v4.13.6",
"v4.13.5",
"v4.13.4",
"v4.13.3",
"v4.13.2",
"v4.13.1",
"v4.13.0",
"v4.12.0",
"v4.11.0",
"v4.10.0",
"v4.9.9",
"v4.9.8",
"v4.9.7",
"v4.9.6",
"v4.9.5",
"v4.9.4",
"v4.9.3",
"v4.9.2",
"v4.9.1",
"v4.9.0",
"v4.8.7",
"v4.8.5",
"v4.8.4",
"v4.8.3",
"v4.8.2",
"v4.8.1",
"v4.8.0",
"v4.7.7",
"v4.7.6",
"v4.7.5",
"v4.7.4",
"v4.7.3",
"v4.7.2",
"v4.7.1",
"v4.7.0",
"v4.6.4",
"v4.6.3",
"v4.6.2",
"v4.6.1",
"v4.6.0",
"v4.5.6",
"v4.5.5",
"v4.5.4",
"v4.5.3",
"v4.5.2",
"v4.5.1",
"v4.4.9",
"v4.4.8",
"v4.4.7",
"v4.4.6",
"v4.4.5",
"v4.4.4",
"v4.4.3",
"v4.4.2",
"v4.4.1",
"v4.4.0",
"v4.3.12",
"v4.3.10",
"v4.3.9",
"v4.3.7",
"v4.3.6",
"v4.3.4",
"v4.3.3",
"v4.3.2",
"v4.3.1",
"v4.3.0",
"v4.2.7",
"v4.2.5",
"v4.2.3",
"v4.2.2",
"v4.2.1",
"v4.2.0",
"v4.1.0",
"v4.0.4",
"v4.0.3",
"v4.0.2",
"v4.0.1",
"v4.0.0",
"v4.0.0-rc.7",
"v4.0.0-rc.6",
"v4.0.0-rc.5",
"v4.0.0-rc.4",
"v4.0.0-rc.3",
"v4.0.0-rc.2",
"v4.0.0-rc.1",
"v4.0.0-rc.0",
"v3.12.4",
"v3.12.3",
"v3.12.2",
"v3.12.1",
"v3.12.0",
"v3.11.16",
"v3.11.15",
"v3.11.14",
"v3.11.13",
"v3.11.12",
"v3.11.10",
"v3.11.9",
"v3.11.8",
"v3.11.7",
"v3.11.6",
"v3.11.5",
"v3.11.4",
"v3.11.3",
"v3.11.2",
"v3.11.1",
"v3.11.0",
"v3.10.8",
"v3.10.7",
"v3.10.6",
"v3.10.5",
"v3.10.4",
"v3.10.2",
"v3.10.1",
"v3.10.0",
"v3.9.6",
"v3.9.5",
"v3.9.4",
"v3.9.3",
"v3.9.2",
"v3.9.0"
]
}
],
"aliases": [
"CVE-2026-82761",
"GHSA-23gr-vcp4-r27q"
],
"credits": [
{
"name": "James Harton",
"type": "REMEDIATION_DEVELOPER"
},
{
"name": "Peter Ullrich",
"type": "REPORTER"
},
{
"name": "Jonatan Männchen / EEF",
"type": "ANALYST"
}
],
"database_specific": {
"capec_ids": [
"CAPEC-29"
],
"cpe_ids": [
"cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
],
"cwe_ids": [
"CWE-367"
]
},
"details": "## Summary\n\nTime-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.\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.",
"id": "EEF-CVE-2026-82761",
"modified": "2026-09-17T13:26:03.671040166Z",
"published": "2026-09-17T13:09:01.534Z",
"references": [
{
"type": "ADVISORY",
"url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-23gr-vcp4-r27q"
},
{
"type": "WEB",
"url": "https://cna.erlef.org/cves/CVE-2026-82761.html"
},
{
"type": "WEB",
"url": "https://github.com/team-alembic/ash_authentication/commit/cf3d227ef25912cf1b0c5fa80f20001f5c46a102"
},
{
"type": "FIX",
"url": "https://github.com/team-alembic/ash_authentication/commit/18dfdb36c14aa6a61df8572bce2d5ec36b1d9840"
},
{
"type": "FIX",
"url": "https://github.com/team-alembic/ash_authentication/commit/9ef6864b8833d3b795427a7b8dc518a4997d41ab"
},
{
"type": "PACKAGE",
"url": "https://hex.pm/packages/ash_authentication"
}
],
"schema_version": "1.9.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Magic link single-use tokens replayable via TOCTOU race in AshAuthentication"
}