# CVE-2026-59249: Other in mint

> A malicious server can desynchronize the Mint HTTP client and intermediaries via chunk-size parsing, poisoning response queues on pooled connections.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/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:** 16 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** EEF-CVE-2026-59249, GHSA-x3x7-96vm-6h2w

## What is CVE-2026-59249?

CVE-2026-59249 is a medium-severity vulnerability in elixir-mint mint, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Inconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on the same pooled connection, enabling response-queue poisoning against subsequent requests that share the connection.

The Mint.HTTP1.decode_body/5 function in lib/mint/http1.ex parses the chunk-size line of a Transfer-Encoding: chunked response with Integer.parse(data, 16). RFC 7230 defines chunk-size = 1*HEXDIG and forbids any sign prefix, but Integer.parse/2 accepts an optional leading + or -. A chunk-size line of +5 is accepted as a five-byte chunk; lines of +0 and -0 are accepted as the terminating zero-length chunk and end the message body early.

An RFC-strict intermediary in the response path rejects these forms, so the intermediary and the Mint client disagree on where one response ends and the next begins. On a pooled keep-alive connection, an attacker-influenced origin can inject bytes that the client attributes to the next legitimate response on the same connection, poisoning the response queue and corrupting the responses returned to unrelated in-flight requests.

This issue affects mint: from 0.1.0 before 1.9.3.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2026-59249?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mint` | Hex | From 0.1.0 | 1.9.3 |

## How do I fix CVE-2026-59249?

Upgrade mint to 1.9.3 or later.

## Is CVE-2026-59249 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59249 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59249 and fix it if it is affected.

What it is: CVE-2026-59249 is a medium-severity vulnerability in elixir-mint mint, published on 16 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-2026-59249 exists.

Affected packages and fixed versions:
- mint (Hex): affected from 0.1.0; fixed in 1.9.3

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-2026-59249/ (Markdown: https://insights.sbomify.com/CVE-2026-59249/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59249
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59249
- OSV: https://osv.dev/vulnerability/CVE-2026-59249

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59249/
Summaries are generated and may contain mistakes; the official description above is the record.