Low 2.4Published Aug 10, 2026

CVE-2026-18503Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()

Updated under an hour ago (Oct 27, 2026, 12:30 AM ET)

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It affects Python Software Foundation CPython. 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

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: 2.4 LOW (v4.0, CNA)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
Weakness (CWE): CWE-1176
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: Awaiting Analysis
Record last updated: Oct 13, 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 3.10.21; from 3.11.0 before 3.11.16; from 3.12.0 before 3.12.14; from 3.13.0 before 3.13.15; from 3.14.0 before 3.14.7; from 3.15.0a1 before 3.15.0rc1; from 3.16.0a1 before 3.16.0	CNA record

References

References

https://mail.python.org/archives/list/security-announce@python.org/thread/KQ7NBMCPAZJHRROQXJQE4GMXGLD5KHBS/	vendor-advisory
https://github.com/python/cpython/pull/153694	patch
https://github.com/python/cpython/issues/98820	issue-tracking
https://github.com/python/cpython/commit/063d4555c94ef412c731527dbf30193327f2ee82	patch
https://github.com/python/cpython/commit/476fb09cdb0d73e645849d98c610e7e5697ce7c9	patch
https://github.com/python/cpython/commit/89f29c760c02774b099ddd6863268eb13fa3946a	patch
https://github.com/python/cpython/commit/b30c7fa9edd921a118f286e9f90f560777fa693b	patch
https://github.com/python/cpython/commit/b09a67a20c464f8288c9f9a6b9c7082a74560024	patch
https://github.com/python/cpython/commit/fd78b565d7c326f96ae903ab945b47f35d829cf4	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.