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CVE-2026-18503
Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
Low2.4EPSS 0.12%
- Published
- Updated
- Reserved
- Assigned by
- PSF
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().
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| PSFCNA (assigner) | 4.0 | Low2.4 | 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 |
| NVDNVD · Awaiting Analysis | 4.0 | Low2.4 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.12% · top 98% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 2.4.
Weakness
Affected products
Python Software Foundation · CPython
- affected < 3.10.21
- affected 3.11.0 – < 3.11.16
- affected 3.12.0 – < 3.12.14
- affected 3.13.0 – < 3.13.15
- affected 3.14.0 – < 3.14.7
- affected 3.15.0a1 – < 3.15.0rc1
- affected 3.16.0a1 – < 3.16.0
References (9)
- https://mail.python.org/archives/list/[email protected]/thread/KQ7NBMCPAZJHRROQXJQE4GMXGLD5KHBS/ (opens in a new tab)vendor-advisory
- https://github.com/python/cpython/pull/153694 (opens in a new tab)patch
- https://github.com/python/cpython/issues/98820 (opens in a new tab)issue-tracking
- https://github.com/python/cpython/commit/063d4555c94ef412c731527dbf30193327f2ee82 (opens in a new tab)patch
- https://github.com/python/cpython/commit/476fb09cdb0d73e645849d98c610e7e5697ce7c9 (opens in a new tab)patch
- https://github.com/python/cpython/commit/89f29c760c02774b099ddd6863268eb13fa3946a (opens in a new tab)patch
- https://github.com/python/cpython/commit/b30c7fa9edd921a118f286e9f90f560777fa693b (opens in a new tab)patch
- https://github.com/python/cpython/commit/b09a67a20c464f8288c9f9a6b9c7082a74560024 (opens in a new tab)patch
- https://github.com/python/cpython/commit/fd78b565d7c326f96ae903ab945b47f35d829cf4 (opens in a new tab)patch
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-18503)Record last updated .