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High severity · published Dec 1, 2025
CVE-2025-13836
Excessive read buffering DoS in http.client
7.5
CVSS
1.6%
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.6% · higher than 76% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CP
CPython · Python Software Foundation
before 3.10.20; 3.11.0 before 3.11.15; 3.12.0 before 3.12.13; 3.13.0 before 3.13.11; 3.14.0 before 3.14.1; 3.15.0a1 before 3.15.0a3 · source: vendor
PY
Python · Python
before 3.10.20; 3.11.0 before 3.11.15; 3.12.0 before 3.12.13; 3.13.0 before 3.13.11; 3.14.0; 3.15.0; +1 more · source: NVD
Affected product
CP
CPython
Python Software Foundation
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-13836
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-13836
Patch
https://github.com/python/cpython/commit/14b1fdb0a94b96f86fc7b86671ea9582b8676628
Patch
https://github.com/python/cpython/commit/289f29b0fe38baf2d7cb5854f4bb573cc34a6a15
Patch
https://github.com/python/cpython/commit/4ce27904b597c77d74dd93f2c912676021a99155
Patch
https://github.com/python/cpython/commit/5a4c4a033a4a54481be6870aa1896fad732555b5
Patch
https://github.com/python/cpython/commit/5dc101675fd22918facbbe0fecdc821502beaaf0
Patch
https://github.com/python/cpython/commit/afc40bdd3dd71f343fd9016f6d8eebbacbd6587c
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