CyberSecBulletin
CVE-2024-25126NVD status: Analyzed

rack: Inefficient Regular Expression Complexity

Published Updated By the CyberSecBulletin desk

CVE-2024-25126 is a high-severity inefficient regular expression complexity vulnerability in rack, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected rack versions: >= 3.0.0, < 3.0.9.1; >= 0.4, < 2.2.8.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 35.4% chance of exploitation within 30 days, which is in the top 1.53% of all scored CVEs.

Patch this week

EPSS places it among the vulnerabilities most likely to be exploited soon.

What to do

  1. Update rack to 3.0.9.1 or 2.2.8.1, whichever matches your release line, or a later version.
  2. Read the advisory on discuss.rubyonrails.org for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Rackrack>= 3.0.0, < 3.0.9.1; >= 0.4, < 2.2.8.1Not stated
Rack Projectrack3.0.0 up to, but not including, 3.0.9.1; 0.4 up to, but not including, 2.2.8.13.0.9.1, 2.2.8.1
DebianDebian Linux10.0Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.15.3MediumCNA (github.com)
CVSS 3.17.5HighNVD

Official description

Rack is a modular Ruby web server interface. Carefully crafted content type headers can cause Rack’s media type parser to take much longer than expected, leading to a possible denial of service vulnerability (ReDos 2nd degree polynomial). This vulnerability is patched in 3.0.9.1 and 2.2.8.1.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Inefficient Regular Expression Complexity

The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.

How developers prevent this class of flaw

  • Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
  • Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
  • Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.

More Inefficient Regular Expression Complexity vulnerabilities (CWE-1333)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Technical write-ups (may include proof of concept)

Other vulnerabilities in rack

All rack vulnerabilities

Recent Inefficient Regular Expression Complexity vulnerabilities

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