CVE-2024-26146Network attack vector

Service interruption via whitespace-regex backtracking

Published Feb 28, 2024 · Updated Feb 13, 2025

ReDoS in affected Rack releases allows remote attackers to interrupt service with crafted Accept or Forwarded headers. Rack::Utils q_values and forwarded_values split attacker-controlled headers with whitespace-matching regular expressions whose backtracking consumes excessive CPU. The request requires no authentication; repeated parsing can exhaust server CPU, while Ruby 3.2 and later mitigate the behavior.

CVSS severity5.3
Medium
EPSS probability2.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

ReDoS in affected Rack releases allows remote attackers to interrupt service with crafted Accept or Forwarded headers. Rack::Utils q_values and forwarded_values split attacker-controlled headers with whitespace-matching regular expressions whose backtracking consumes excessive CPU. The request requires no authentication; repeated parsing can exhaust server CPU, while Ruby 3.2 and later mitigate the behavior.

The record

CVE
CVE-2024-26146
Published
Feb 28, 2024
Updated
Feb 13, 2025
Vendor
Rack
Product
Rack
Classifications
CWE-1333, CAPEC-492, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 28, 2024CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2025Record 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=0 <2.0.9.4
  2. Affected versionversion=< 2.0.9.4
  3. Affected versionversion=>= 2.1.0, < 2.1.4.4
  4. Affected versionversion=2.1.0 <2.1.4.4
  5. Affected versionversion=>= 2.2.0, < 2.2.8.1
  6. Affected versionversion=2.2.0 <2.2.8.1
  7. Affected versionversion=>= 3.0.0, < 3.0.9.1
  8. Affected versionversion=3.0.0 <3.0.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rack · Rackversion=0 <2.0.9.4; version=< 2.0.9.4; version=>= 2.1.0, < 2.1.4.4; version=2.1.0 <2.1.4.4; version=>= 2.2.0, < 2.2.8.1; version=2.2.0 <2.2.8.1; version=>= 3.0.0, < 3.0.9.1; version=3.0.0 <3.0.9.1

Published CVSS scores

5.3GitHub CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
CAPEC-492Regular Expression Exponential Blowup
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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