CVE-2026-53431

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.

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Weakness Type (CWE)

CWE-294 CWE-294

References

Other References

https://cna.erlef.org/cves/CVE-2026-53431.html https://github.com/malach-it/boruta_auth/commit/5204f88f9b2cdd9637a755337ed5f99185be5474 https://github.com/malach-it/boruta_auth/commit/69363432aa36760fc5438e4e17115d0f7c1b925a https://github.com/malach-it/boruta_auth/security/advisories/GHSA-xjv8-vmh5-xhf6 https://osv.dev/vulnerability/EEF-CVE-2026-53431 https://github.com/malach-it/boruta_auth/security/advisories/GHSA-xjv8-vmh5-xhf6

Frequently Asked Questions

What is CVE-2026-53431? +

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.

How do I check if I'm vulnerable to CVE-2026-53431? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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