CVE-2026-53431
Boruta accepts expired JWT client assertions due to missing exp claim validation
- Published
- Updated
- Reserved
- Assigned by
- EEF
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.
Public exploit
A reference of the record is tagged as an exploit or proof of concept: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.
- https://github.com/malach-it/boruta_auth/security/advisories/GHSA-xjv8-vmh5-xhf6 (opens in a new tab)vendor-advisoryrelatedexploit
Timeline
ID reserved
By EEF
- 51 days later
· 51 days later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| EEFCNA (assigner) | 4.0 | Critical9.1 | 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 |
| NVDNVD · Deferred | 4.0 | Critical9.1 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.51% · top 56% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.1.
Weakness
Affected products
What to do
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.
References (5)
- https://github.com/malach-it/boruta_auth/security/advisories/GHSA-xjv8-vmh5-xhf6 (opens in a new tab)vendor-advisoryrelatedexploit
- https://cna.erlef.org/cves/CVE-2026-53431.html (opens in a new tab)related
- https://osv.dev/vulnerability/EEF-CVE-2026-53431 (opens in a new tab)related
- https://github.com/malach-it/boruta_auth/commit/5204f88f9b2cdd9637a755337ed5f99185be5474 (opens in a new tab)patch
- https://github.com/malach-it/boruta_auth/commit/69363432aa36760fc5438e4e17115d0f7c1b925a (opens in a new tab)patch
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-53431)Record last updated .