Medium 6.3Published Dec 1, 2025

CVE-2025-13836Excessive read buffering DoS in http.client

Updated under an hour ago (Oct 27, 2026, 6:30 AM ET)

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It affects Python Software Foundation CPython and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Python Software Foundation CPython

Exploited in the last 30 days

When reading an HTTP response from a server, if no read amount is specified, the default behavior will be to use Content-Length. This allows a malicious server to cause the client to read large amounts of data into memory, potentially causing OOM or other DoS.

CVSS: 6.3 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L
Weakness (CWE): CWE-400
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: PSF
NVD analysis: Analyzed
Record last updated: Mar 3, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Python Software Foundation CPython python_software_foundation:cpython (from the name)	before 3.10.20; from 3.11.0 before 3.11.15; from 3.12.0 before 3.12.13; from 3.13.0 before 3.13.11; from 3.14.0 before 3.14.1; from 3.15.0a1 before 3.15.0a3	CNA record
python python python:python	before 3.10.20; from 3.11.0 before 3.11.15; from 3.12.0 before 3.12.13; from 3.13.0 before 3.13.11; 3.14.0; 3.15.0; 3.15.0	NVD

References

References

https://github.com/python/cpython/issues/119451	issue-tracking, patch
https://github.com/python/cpython/pull/119454	patch, issue-tracking
https://github.com/python/cpython/commit/4ce27904b597c77d74dd93f2c912676021a99155	patch
https://github.com/python/cpython/commit/5a4c4a033a4a54481be6870aa1896fad732555b5	patch
https://mail.python.org/archives/list/security-announce@python.org/thread/OQ6G7MKRQIS3OAREC3HNG3D2DPOU34XO/	vendor-advisory
https://github.com/python/cpython/commit/289f29b0fe38baf2d7cb5854f4bb573cc34a6a15	patch
https://github.com/python/cpython/commit/14b1fdb0a94b96f86fc7b86671ea9582b8676628	patch
https://github.com/python/cpython/commit/5dc101675fd22918facbbe0fecdc821502beaaf0	patch
https://github.com/python/cpython/commit/afc40bdd3dd71f343fd9016f6d8eebbacbd6587c	patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.