CVE-2026-82761

Estado: AplazadaCrítica (9.1)—

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.

Leer descripción completaMostrar menos

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.

CVSS

Versión: 4.0
Vector: 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Puntuación base: 9.1

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.56%
Percentil entre todas las CVEs puntuadas: 45
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access85 %
Impacto principalT1078.001 Default Accountsstealth · persistence · privilege escalation · initial access80 %
Impacto secundarioT1550.001 Application Access Tokenlateral movement75 %

TOCTOU en validación de magic link permite reutilización de token de un único uso. AV:N/AC:L/AT:P sin autenticación previa permite explotación remota de aplicación expuesta. El atacante obtiene autenticación legítima como usuario objetivo.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Application Developer Guidance Vulnerability Scanning Restrict Web-Based Content Privileged Account Management Password Policies Network Segmentation

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Alembic — ASH Authentication^AI

CWE

CWE-367

Referencias

JSON original (NVD)

Mostrar

{
  "id": "CVE-2026-82761",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-82761",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-17T18:25:13.930894Z"
        }
      }
    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 9.1,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
          "subIntegrityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "affectedData": [
        {
          "cpes": [
            "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/team-alembic/ash_authentication",
          "vendor": "team-alembic",
          "modules": [
            "'Elixir.AshAuthentication.Strategy.MagicLink.SignInPreparation'",
            "'Elixir.AshAuthentication.Strategy.MagicLink.SignInChange'",
            "'Elixir.AshAuthentication.TokenResource.Actions'"
          ],
          "product": "ash_authentication",
          "versions": [
            {
              "status": "affected",
              "version": "3.9.0",
              "lessThan": "4.15.0",
              "versionType": "semver"
            },
            {
              "status": "affected",
              "version": "5.0.0-rc.0",
              "lessThan": "5.0.0-rc.14",
              "versionType": "semver"
            }
          ],
          "packageURL": "pkg:hex/ash_authentication",
          "packageName": "ash_authentication",
          "programFiles": [
            "lib/ash_authentication/strategies/magic_link/sign_in_preparation.ex",
            "lib/ash_authentication/strategies/magic_link/sign_in_change.ex",
            "lib/ash_authentication/token_resource/actions.ex"
          ],
          "collectionURL": "https://repo.hex.pm",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "'Elixir.AshAuthentication.Strategy.MagicLink.SignInPreparation':prepare/3"
            },
            {
              "name": "'Elixir.AshAuthentication.Strategy.MagicLink.SignInChange':change/3"
            },
            {
              "name": "'Elixir.AshAuthentication.TokenResource.Actions':revoke/3"
            }
          ]
        },
        {
          "cpes": [
            "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"
          ],
          "repo": "https://github.com/team-alembic/ash_authentication",
          "vendor": "team-alembic",
          "modules": [
            "'Elixir.AshAuthentication.Strategy.MagicLink.SignInPreparation'",
            "'Elixir.AshAuthentication.Strategy.MagicLink.SignInChange'",
            "'Elixir.AshAuthentication.TokenResource.Actions'"
          ],
          "product": "ash_authentication",
          "versions": [
            {
              "status": "affected",
              "changes": [
                {
                  "at": "18dfdb36c14aa6a61df8572bce2d5ec36b1d9840",
                  "status": "unaffected"
                },
                {
                  "at": "9ef6864b8833d3b795427a7b8dc518a4997d41ab",
                  "status": "unaffected"
                }
              ],
              "version": "cf3d227ef25912cf1b0c5fa80f20001f5c46a102",
              "lessThan": "*",
              "versionType": "git"
            }
          ],
          "packageURL": "pkg:github/team-alembic/ash_authentication",
          "packageName": "team-alembic/ash_authentication",
          "programFiles": [
            "lib/ash_authentication/strategies/magic_link/sign_in_preparation.ex",
            "lib/ash_authentication/strategies/magic_link/sign_in_change.ex",
            "lib/ash_authentication/token_resource/actions.ex"
          ],
          "collectionURL": "https://github.com",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "'Elixir.AshAuthentication.Strategy.MagicLink.SignInPreparation':prepare/3"
            },
            {
              "name": "'Elixir.AshAuthentication.Strategy.MagicLink.SignInChange':change/3"
            },
            {
              "name": "'Elixir.AshAuthentication.TokenResource.Actions':revoke/3"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-09-17T14:17:33.423",
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-82761.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/team-alembic/ash_authentication/commit/18dfdb36c14aa6a61df8572bce2d5ec36b1d9840",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/team-alembic/ash_authentication/commit/9ef6864b8833d3b795427a7b8dc518a4997d41ab",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/team-alembic/ash_authentication/commit/cf3d227ef25912cf1b0c5fa80f20001f5c46a102",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-23gr-vcp4-r27q",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-82761",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "description": [
        {
          "lang": "en",
          "value": "CWE-367"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "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'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."
    }
  ],
  "lastModified": "2026-09-18T18:16:18.527",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}