What’s Vulnerable › Vulnerabilities

CVE-2025-6075: Quadratic complexity in os.path.expandvars() with user-controlled template

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-10-31 · updated 2026-10-07
• Weakness: CWE-400

Description

If the value passed to os.path.expandvars() is user-controlled a performance degradation is possible when expanding environment variables.

Affected products

• Python: before 3.9.0; from 3.13.1 before 3.13.11; from 3.14.0 before 3.14.1; 3.15.0-alpha1 — fixed in 3.13.11, 3.14.1, 3.9.0

How to fix

Upgrade to a fixed version: Python 3.13.11, 3.14.1, 3.9.0. Check the vendor advisory for mitigations.

References

• https://github.com/python/cpython/commit/2e6150adccaaf5bd95d4c19dfd04a36e0b325d8c
• https://github.com/python/cpython/commit/5dceb93486176e6b4a6d9754491005113eb23427
• https://github.com/python/cpython/commit/631ba3407e3348ccd56ce5160c4fb2c5dc5f4d84
• https://github.com/python/cpython/commit/892747b4cf0f95ba8beb51c0d0658bfaa381ebca
• https://github.com/python/cpython/commit/9ab89c026aa9611c4b0b67c288b8303a480fe742
• https://github.com/python/cpython/commit/c8a5f3435c342964e0a432cc9fb448b7dbecd1ba
• https://github.com/python/cpython/commit/f029e8db626ddc6e3a3beea4eff511a71aaceb5c
• https://github.com/python/cpython/issues/136065
• https://mail.python.org/archives/list/security-announce@python.org/thread/IUP5QJ6D4KK6ULHOMPC7DPNKRYQTQNLA/

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