CyberSecBulletin
CVE-2025-8194NVD status: Deferred

CPython: Loop with Unreachable Exit Condition

Published Updated By the CyberSecBulletin desk

CVE-2025-8194 is a high-severity loop with unreachable exit condition 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 3.9.24, 3.10.19, 3.11.14 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 0.76% chance of exploitation within 30 days, higher than 56% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update CPython to 3.9.24 or 3.10.19 or 3.11.14 or 3.12.12, whichever matches your release line, or a later version.
  2. 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 3.9.24; 3.10.0 up to, but not including, 3.10.19; 3.11.0 up to, but not including, 3.11.14; 3.12.0 up to, but not including, 3.12.12; 3.13.0 up to, but not including, 3.13.6; 3.14.0a1 up to, but not including, 3.14.0rc23.9.24, 3.10.19, 3.11.14, 3.12.12, 3.13.6, 3.14.0rc2

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 CNA (python.org).

Official description

There is a defect in the CPython “tarfile” module affecting the “TarFile” extraction and entry enumeration APIs. The tar implementation would process tar archives with negative offsets without error, resulting in an infinite loop and deadlock during the parsing of maliciously crafted tar archives. This vulnerability can be mitigated by including the following patch after importing the “tarfile” module: https://gist.github.com/sethmlarson/1716ac5b82b73dbcbf23ad2eff8b33e1

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

The underlying weakness: Loop with Unreachable Exit Condition

The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

More Loop with Unreachable Exit Condition vulnerabilities (CWE-835)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in CPython

All CPython vulnerabilities

Recent Loop with Unreachable Exit Condition vulnerabilities

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