CVE-2026-53431

Summary

Authentication Bypass by Capture-replay vulnerability in malach-it Boruta allows an attacker who has obtained a previously valid JWT client assertion to authenticate as the issuing OAuth client after the assertion has expired.

Boruta accepts JWT-based client authentication (client_secret_jwt and private_key_jwt token endpoint authentication methods) but never enforces that the assertion's exp claim is in the future. The pre-check helper Boruta.Oauth.Request.Base.check_expiration/1 in lib/boruta/oauth/request/base.ex only verifies that an exp claim is present (it pattern-matches on the existence of the key and returns success), and the Joken token configuration used for signature verification, Boruta.Oauth.Authorization.Client.Token.token_config/0 in lib/boruta/oauth/authorization/client.ex, returns an empty map, so Joken's default exp claim validator is not engaged either. Any attacker who obtains a validly-signed client assertion (for example through logs, reverse proxies, browser tooling, or other observability surfaces) can replay it indefinitely to authenticate as the client and obtain access tokens with that client's privileges.

This issue affects boruta: from 2.3.0 before 2.3.7.

Affected Software

VendorProductVersion RangeStatus
malach-itboruta2.3.0 < 2.3.7affected
malach-itboruta5bfbe1c5443bffe71cf1bf954bbdff61327d9a83 < *affected

Weaknesses

  • CWE-294: CWE-294 Authentication Bypass by Capture-replay

Workarounds

Restrict the use of JWT-based client authentication (client_secret_jwt and private_key_jwt) to highly trusted clients, and prefer non-JWT client authentication methods (client_secret_basic or client_secret_post) where possible. Where JWT client authentication must remain enabled, issue short-lived client assertions and protect them from exposure in application logs, fronting proxies, browser tooling, and observability systems to reduce the window for replay.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: no
    • Technical Impact: total

Additional References

References