CVE-2024-39316Network attack vector

Service interruption via inefficient Accept-header regexes

Published Jul 2, 2024 · Updated Aug 2, 2024

Regular expression denial of service in Rack 3.1.0 through 3.1.4 allows remote authenticated users to interrupt service via crafted Accept headers. Rack::Request::Helpers parse_http_accept_header uses whitespace-trimming regular expressions as comma and semicolon split delimiters, so crafted Accept-Encoding or Accept-Language values trigger excessive matching work. Any application that invokes this helper on attacker-controlled headers exposes CPU time, while the documented impact is limited to service availability.

CVSS severity6.5
Medium
EPSS probability0.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Rack 3.1.0 through 3.1.4 allows remote authenticated users to interrupt service via crafted Accept headers. Rack::Request::Helpers parse_http_accept_header uses whitespace-trimming regular expressions as comma and semicolon split delimiters, so crafted Accept-Encoding or Accept-Language values trigger excessive matching work. Any application that invokes this helper on attacker-controlled headers exposes CPU time, while the documented impact is limited to service availability.

The record

CVE
CVE-2024-39316
Published
Jul 2, 2024
Updated
Aug 2, 2024
Vendor
Rack
Product
Rack
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 2, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.1.0, < 3.1.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Rack · Rackversion=>= 3.1.0, < 3.1.5

Published CVSS scores

6.5GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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