# 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.

- **Severity:** Critical 9.1 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 30 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** EEF-CVE-2026-53431, GHSA-xjv8-vmh5-xhf6

## 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 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2026-53431?

1 open source package ship an affected version, including boruta.


| Package | Ecosystem | 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.

## Is CVE-2026-53431 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53431 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53431 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53431 exists.

Affected packages and fixed versions:
- boruta (Hex): affected from 2.3.0; fixed in 2.3.7

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53431/ (Markdown: https://insights.sbomify.com/CVE-2026-53431/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53431
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53431
- OSV: https://osv.dev/vulnerability/CVE-2026-53431

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53431/
Summaries are generated and may contain mistakes; the official description above is the record.