CPython up to 3.13.x tarfile infinite loop

Summaryinfo

A vulnerability was found in CPython up to 3.13.x. It has been rated as problematic. The affected element is an unknown function of the component tarfile Module. Performing a manipulation results in infinite loop. This vulnerability is identified as CVE-2025-8194. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic has been found in CPython up to 3.13.x. This affects an unknown function of the component tarfile Module. The manipulation with an unknown input leads to a infinite loop vulnerability. CWE is classifying the issue as CWE-835. The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. This is going to have an impact on availability. The summary by CVE is:

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: import tarfile def _block_patched(self, count):     if count < 0: # pragma: no cover         raise tarfile.InvalidHeaderError("invalid offset")     return _block_patched._orig_block(self, count) _block_patched._orig_block = tarfile.TarInfo._block tarfile.TarInfo._block = _block_patched

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2025-8194 since 07/25/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 243944 (openSUSE 15 Security Update : python39 (SUSE-SU-2025:02700-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.14.0 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (243944) and CERT Bund (WID-SEC-2025-1664). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Fedora Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• Open Source Python
• IBM App Connect Enterprise
• Dell Secure Connect Gateway

Productinfo

Type

• Programming Language Software

Name

• CPython

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9
• 3.10
• 3.11
• 3.12
• 3.13

CPE 2.3info

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CPE 2.2info

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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