# CVE-2024-39316: Rack ReDoS Vulnerability in HTTP Accept Headers Parsing

> Attackers can cause Denial of Service in Rack applications by sending crafted HTTP Accept headers that trigger excessive processing time.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Jul 2024
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-cj83-2ww7-mvq7

## What is CVE-2024-39316?

CVE-2024-39316 is a medium-severity denial of service vulnerability in rack, published on 2 Jul 2024. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Rack is a modular Ruby web server interface. Starting in version 3.1.0 and prior to version 3.1.5, Regular Expression Denial of Service (ReDoS) vulnerability exists in the `Rack::Request::Helpers` module when parsing HTTP Accept headers. This vulnerability can be exploited by an attacker sending specially crafted `Accept-Encoding` or `Accept-Language` headers, causing the server to spend excessive time processing the request and leading to a Denial of Service (DoS). The fix for CVE-2024-26146 was not applied to the main branch and thus while the issue was fixed for the Rack v3.0 release series, it was not fixed in the v3.1 release series until v3.1.5. Users of versions on the 3.1 branch should upgrade to version 3.1.5 to receive the fix.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2024-39316?

2 open source packages ship an affected version, including rack. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `rack` | RubyGems | From 3.1.0 | 3.1.5 |
| `rack` | RubyGems | From 3.1.0 | 3.1.5 |

Products: Rack Rack.

## How do I fix CVE-2024-39316?

Upgrade rack to 3.1.5 or later.

## Is CVE-2024-39316 being exploited?

There is no known exploitation of CVE-2024-39316 in the wild and no public exploit code.

## Other vulnerabilities in rack

- [CVE-2026-34785](https://insights.sbomify.com/CVE-2026-34785/): Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching (high 7.5)
- [CVE-2026-34827](https://insights.sbomify.com/CVE-2026-34827/): Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser (high 7.5)
- [CVE-2026-34829](https://insights.sbomify.com/CVE-2026-34829/): Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length (high 7.5)
- [CVE-2026-22860](https://insights.sbomify.com/CVE-2026-22860/): Rack has a Directory Traversal via Rack:Directory (high 7.5)
- [CVE-2025-61919](https://insights.sbomify.com/CVE-2025-61919/): Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-39316 and fix it if it is affected.

What it is: CVE-2024-39316 is a medium-severity denial of service vulnerability in rack, published on 2 Jul 2024. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-39316 in the wild and no public exploit code.

Affected packages and fixed versions:
- rack (RubyGems): affected from 3.1.0; fixed in 3.1.5
- rack (RubyGems): affected from 3.1.0; fixed in 3.1.5

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-2024-39316/ (Markdown: https://insights.sbomify.com/CVE-2024-39316/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-39316
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-39316
- OSV: https://osv.dev/vulnerability/CVE-2024-39316

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-39316/
Summaries are generated and may contain mistakes; the official description above is the record.