# CVE-2026-82729: Quadratic chunk-size parsing in Mint.HTTP1.Parse allows CPU-exhaustion DoS

> A remote HTTP server can cause CPU exhaustion and denial of service in the Mint HTTP/1 client by sending excessively long chunk-size fields.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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:** 4 Sep 2026
- **Updated:** 4 Sep 2026
- **Also known as:** EEF-CVE-2026-82729, GHSA-7p8w-j234-7qc8

## What is CVE-2026-82729?

CVE-2026-82729 is a medium-severity denial of service vulnerability in elixir-mint mint, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Inefficient Algorithmic Complexity vulnerability in elixir-mint mint allows a remote HTTP server to exhaust CPU on the client host and cause a denial of service.

parse_hex_prefix/2 in lib/mint/http1/parse.ex folds each hex digit of a chunked response's chunk-size field into an arbitrary-precision accumulator with acc * 16 + digit and imposes no limit on the digit count. Because the accumulator grows without bound, the multiplication is not constant time and one pass over N digits costs O(N squared). handle_data/2 prepends conn.buffer and re-parses from the start on every socket message, so a server that dribbles the digits out in small packets makes the client pay that cost repeatedly. A run of roughly 512,000 hex digits costs over ten seconds of CPU in a single pass, measured on stock defaults. The parser reaches this state after a valid status line and a complete, valid header section, so an intermediary inspecting only headers sees an ordinary 200 response.

This issue affects mint: from 1.9.3 before 1.10.0.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-82729?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mint` | Hex | From 1.9.3 | 1.10.0 |

## How do I fix CVE-2026-82729?

Upgrade mint to 1.10.0 or later.

## Is CVE-2026-82729 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-82729 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82729 and fix it if it is affected.

What it is: CVE-2026-82729 is a medium-severity denial of service vulnerability in elixir-mint mint, published on 4 Sep 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-2026-82729 exists.

Affected packages and fixed versions:
- mint (Hex): affected from 1.9.3; fixed in 1.10.0

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-2026-82729/ (Markdown: https://insights.sbomify.com/CVE-2026-82729/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82729
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82729
- OSV: https://osv.dev/vulnerability/CVE-2026-82729

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82729/
Summaries are generated and may contain mistakes; the official description above is the record.