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MEDIUM severity

CVE-2024-39316 — rack

MEDIUMFix: rack/rack@412c980

CVE-2024-39316 is a medium-severity (CVSS 6.5) CWE-1333 vulnerability in rack. A fix is available for rack — see the affected versions and patch details below.

Rack ReDoS Vulnerability in HTTP Accept Headers Parsing

Also known asGHSA-cj83-2ww7-mvq7
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2024-39316.

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs59th percentile — riskier than 59% of all scored CVEsHighest risk
0.33%0.67%1.01%1.36%0.8%0.9%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
💎rack

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemsrack≥ 3.1.0&&< 3.1.53.1.5bundle update rack --conservative

Affected Products

1 product · 1 configurations
Application
rackrack
≥ 3.1.0 && < 3.1.5
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update rack to 3.1.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-39316 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

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
O3 Security · Impact-Aware SCA

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CVE-2024-39316: rack DoS — Fixed in 3.1.5