CVE-2026-18503: low-severity vulnerability in Python Software Foundation CPython
Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
Published · Updated
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8Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 2.4epss 0.1%
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().
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Affected products
Python Software Foundation · CPythonRelated CVEs — Python Software Foundation CPython
In the same product, most dangerous first.
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References
https://github.com/python/cpython/commit/063d4555c94ef412c731527dbf30193327f2ee82https://github.com/python/cpython/commit/476fb09cdb0d73e645849d98c610e7e5697ce7c9https://github.com/python/cpython/commit/89f29c760c02774b099ddd6863268eb13fa3946ahttps://github.com/python/cpython/commit/b09a67a20c464f8288c9f9a6b9c7082a74560024https://github.com/python/cpython/commit/b30c7fa9edd921a118f286e9f90f560777fa693bhttps://github.com/python/cpython/commit/fd78b565d7c326f96ae903ab945b47f35d829cf4https://github.com/python/cpython/issues/98820https://github.com/python/cpython/pull/153694https://mail.python.org/archives/list/security-announce@python.org/thread/KQ7NBMCPAZJHRROQXJQE4GMXGLD5KHBS/