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Low severity · published Aug 10, 2026
CVE-2026-18503
Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
2.4
CVSS
0.1%
EPSS
No
On KEV
Description
Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialect sniffing and consume significant CPU when applications pass unbounded input to csv.Sniffer.sniff().
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 2% 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 3.10.21; 3.11.0 before 3.11.16; 3.12.0 before 3.12.14; 3.13.0 before 3.13.15; 3.14.0 before 3.14.7; 3.15.0a1 before 3.15.0rc1; +1 more · source: vendor
Affected product
CP
CPython
Python Software Foundation
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-18503
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-18503
vendor-advisory
https://mail.python.org/archives/list/security-announce@python.org/thread/KQ7NBMCPAZJHRROQXJQE4GMXGLD5KHBS/
patch
https://github.com/python/cpython/pull/153694
issue-tracking
https://github.com/python/cpython/issues/98820
patch
https://github.com/python/cpython/commit/063d4555c94ef412c731527dbf30193327f2ee82
patch
https://github.com/python/cpython/commit/476fb09cdb0d73e645849d98c610e7e5697ce7c9
patch
https://github.com/python/cpython/commit/89f29c760c02774b099ddd6863268eb13fa3946a
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