CVE-2026-53431 Boruta accepts expired JWT client assertions due to missing exp claim validation
Attackers can replay expired JWT client assertions to authenticate as OAuth clients and obtain access tokens due to missing expiration validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53431?
CVE-2026-53431 is a critical authentication bypass vulnerability in malach-it boruta, published on 30 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-294
Which versions are affected by CVE-2026-53431?
1 open source package ship an affected version, including boruta.
| Package | Affected | Fixed in |
|---|---|---|
boruta Hex | From 2.3.0 | 2.3.7 |
How do I fix CVE-2026-53431?
Upgrade boruta to 2.3.7 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-53431 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53431 exists.
Sources
Also known as EEF-CVE-2026-53431, GHSA-xjv8-vmh5-xhf6.