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.
Published: 2026-07-30
Score: 9.1 Critical
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

Vendor Workaround

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.

Tracking

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Advisories

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History

Thu, 30 Jul 2026 15:00:00 +0000

Type Values Removed Values Added
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.
Title Boruta accepts expired JWT client assertions due to missing exp claim validation
First Time appeared Malach-it
Malach-it boruta Auth
Weaknesses CWE-294
CPEs cpe:2.3:a:malach-it:boruta_auth:*:*:*:*:*:*:*:*
Vendors & Products Malach-it
Malach-it boruta Auth
References
Metrics cvssV4_0

{'score': 9.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}


Subscriptions

Malach-it Boruta Auth
cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-07-30T16:13:22.708Z

Reserved: 2026-06-09T11:01:47.529Z

Link: CVE-2026-53431

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-294

    Authentication Bypass by Capture-replay