CyberSecBulletin
CVE-2024-7592NVD status: Modified

CPython: Inefficient Regular Expression Complexity

Published Updated By the CyberSecBulletin desk

CVE-2024-7592 is a high-severity inefficient regular expression complexity vulnerability in CPython from Python Software Foundation, 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. The record lists versions 3.8.20, 3.9.20, 3.10.15 as the first without the flaw, so updating CPython to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 2.3% chance of exploitation within 30 days, higher than 84% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update CPython to 3.8.20 or 3.9.20 or 3.10.15 or 3.11.10, whichever matches your release line, or a later version.
  2. Update cpython to 3.8.20 or 3.9.20 or 3.10.15 or 3.11.10, whichever matches your release line, or a later version.
  3. Update Python to 3.8.20 or 3.9.20 or 3.10.15 or 3.11.10, whichever matches your release line, or a later version.
  4. 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
Python Software FoundationCPythonbefore 3.8.20; 3.9.0 up to, but not including, 3.9.20; 3.10.0 up to, but not including, 3.10.15; 3.11.0 up to, but not including, 3.11.10; 3.12.0 up to, but not including, 3.12.6; 3.13.0a1 up to, but not including, 3.13.0rc23.8.20, 3.9.20, 3.10.15, 3.11.10, 3.12.6, 3.13.0rc2
Pythoncpythonbefore 3.8.20; 3.9.0 up to, but not including, 3.9.20; 3.10.0 up to, but not including, 3.10.15; 3.11.0 up to, but not including, 3.11.10; 3.12.0 up to, but not including, 3.12.6; 3.13.0a1 up to, but not including, 3.13.0rc23.8.20, 3.9.20, 3.10.15, 3.11.10, 3.12.6, 3.13.0rc2
PythonPythonbefore 3.8.20; 3.9.0 up to, but not including, 3.9.20; 3.10.0 up to, but not including, 3.10.15; 3.11.0 up to, but not including, 3.11.10; 3.12.0 up to, but not including, 3.12.6; 3.13.03.8.20, 3.9.20, 3.10.15, 3.11.10, 3.12.6

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 3.17.5HighNVD
CVSS 3.17.5HighCISA (ADP)

Official description

There is a LOW severity vulnerability affecting CPython, specifically the 'http.cookies' standard library module. When parsing cookies that contained backslashes for quoted characters in the cookie value, the parser would use an algorithm with quadratic complexity, resulting in excess CPU resources being used while parsing the value.

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

Other vulnerabilities in CPython

All CPython vulnerabilities

Recent Inefficient Regular Expression Complexity vulnerabilities

Spotted an error? Tell us.