# CVE-2026-118505: AshAuthentication brute_force_strategy does not limit sign-in and request actions defined on the resource

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

Improper Restriction of Excessive Authentication Attempts vulnerability in team-alembic ash_authentication allows an unauthenticated attacker to guess passwords and one-time passwords without limit.

The password, magic link and OTP strategies enforce brute_force_strategy by adding a preparation only to the actions they generate. When the resource defines one of those actions itself, the strategy uses it as written and nothing checked that it carried the preparation, so the setting compiled and applied no limit. The generators produce exactly this: mix ash_authentication.install writes sign_in_with_password, request_password_reset_token and request_magic_link, mix ash_authentication.upgrade then adds brute_force_strategy to those strategies, and mix ash_authentication.add_strategy.otp writes its OTP actions without the preparation. Separately, with registration_enabled? true the OTP sign-in is a create action, which preparations do not run on, so brute_force_strategy {:preparation, module} never applied to it.

This issue affects ash_authentication: from 5.0.0-rc.4 before 5.0.0-rc.16.

## Remediation

- workaround: Add the brute-force preparation to each protected action defined on the resource, or remove the action so the strategy generates it. For brute_force_strategy {:audit_log, name} that is prepare {AshAuthentication.AddOn.AuditLog.IdentityBruteForcePreparation, action_name: <action>} on the password sign-in, password reset request, magic link request and OTP request actions, and prepare {AshAuthentication.AddOn.AuditLog.BruteForcePreparation, action_name: <action>} on a read OTP sign-in action. For {:preparation, MyModule} it is prepare MyModule. For OTP with registration_enabled? true, switch to brute_force_strategy :rate_limit. (source: CNA: EEF)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: EEF) — https://github.com/team-alembic/ash_authentication/commit/7117b5da5b73ee4cdb372e4adfbaff409b527125

## Affected products and versions

- team-alembic / ash_authentication (ash_authentication): ≥ 5.0.0-rc.4; < 5.0.0-rc.16 (affected, semver). Source: CNA: EEF
- team-alembic / ash_authentication (team-alembic/ash_authentication): ≥ 800caa0d4a5bee1f28ad427f4c12fab72003a577; < 7117b5da5b73ee4cdb372e4adfbaff409b527125 (affected, git). Source: CNA: EEF

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N; source: CNA: EEF

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-307

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-55gf-3263-4r39 (CNA: EEF; vendor-advisory, related)

- https://cna.erlef.org/cves/CVE-2026-118505.html (CNA: EEF; related)

- https://osv.dev/vulnerability/EEF-CVE-2026-118505 (CNA: EEF; related)

- https://github.com/team-alembic/ash_authentication/commit/800caa0d4a5bee1f28ad427f4c12fab72003a577 (CNA: EEF; related)

- https://github.com/team-alembic/ash_authentication/commit/7117b5da5b73ee4cdb372e4adfbaff409b527125 (CNA: EEF; patch)

## Provenance

- CNA: EEF: https://www.cve.org/CVERecord?id=CVE-2026-118505; retrieved 2026-11-03; source updated 2026-11-03

Revision: e883b9304b82531d937cd2d907581f7d0845ed7fbb278603f8d5922d0af60989

Canonical: https://y2.dev/cve/CVE-2026-118505

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