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🛡️ CVE-2026-49757 — ash-authentication

⚪ Unknown ✅ No Known Exploit CWE-290 NVD
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

OAuth2/OIDC account takeover in AshAuthentication via email-based user matching

Summary

Authentication Bypass by Spoofing vulnerability in team-alembic AshAuthentication allows account takeover of local users via OAuth2/OIDC sign-in.

AshAuthentication's OAuth2 and OIDC family strategies matched the local user by email address (an upsert on the email field, or a user-defined sign-in filter) rather than by the OpenID Connect iss/sub claim combination. Per OpenID Connect Core §5.7, only iss/sub uniquely and stably identifies an end-user; other claims, including email, MUST NOT be used as unique identifiers.

A provider login presenting a victim's email, including an unverified email, a reused email, or an account with email\_verified: false, resolved to and signed in as the victim's existing local account. An unauthenticated attacker who can register an account on any accepted OAuth provider with the victim's email (or who benefits from provider-side email reuse or reclamation) obtains the victim's full local privileges.

The fix resolves users by the (strategy, sub) identity stored in a user identity resource, and only links a new sub to an existing local account by email when the provider's email\_verified claim is trusted (trust\_email\_verified?).

This issue affects ash\_authentication from 0.1.0 before 4.14.0 and from 5.0.0-rc.0 before 5.0.0-rc.10.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Attack requirements: Present — the target has to be in a particular state for the attack to work.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-49757 is classified as CWE-290: Authentication Bypass by Spoofing. Identity is inferred from something an attacker can forge, such as a header or address.

Affected software

CVE-2026-49757 is recorded against 2 packages.

  • ash-authentication
  • unknown

Timeline and source

Published on 15 June 2026 and last revised on 30 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Advisory)
cna.erlef.org (Web)
github.com (Fix)
github.com (Fix)
hex.pm (Package)

Other advisories for this package

ash-authentication has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-290: Authentication Bypass by Spoofing) in other software:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CWE CWE-290
Public Exploit ✅ No
Source NVD
Published 2026-06-15
Updated 2026-08-20
Modified 2026-07-30

Affected Packages

Software From version Fixed in
ash-authentication — —
unknown — —

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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