Low
Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
Type: advisorySources: OSV
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().
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-18503
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 4 Nov 2026, 04:07 UTC · Revision 1
Source evidence
Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
core-osv · Original sourcePublished 10 Aug 2026, 13:45 UTC
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().
osv:CVE-2026-18503
Complete source record
{
"id": "f58aeee16281c52516614b311ccdcedecad5b5fcec784116cdb983bec208b255",
"url": "https://osv.dev/vulnerability/CVE-2026-18503",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()",
"summary": "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().",
"evidence": "osv:CVE-2026-18503",
"products": [],
"severity": "low",
"structured": {
"id": "CVE-2026-18503",
"aliases": [
"BIT-libpython-2026-18503",
"BIT-python-2026-18503",
"BIT-python-min-2026-18503",
"CVE-2026-18503",
"PSF-2026-35"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "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"
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],
"modified": "2026-10-28T02:30:33.077210486Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/18xxx/CVE-2026-18503.json",
"https://mail.python.org/archives/list/security-announce@python.org/thread/KQ7NBMCPAZJHRROQXJQE4GMXGLD5KHBS/",
"https://nvd.nist.gov/vuln/detail/CVE-2026-18503",
"https://github.com/python/cpython/issues/98820",
"https://github.com/python/cpython/commit/063d4555c94ef412c731527dbf30193327f2ee82",
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"provider_metadata": {
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"evidence": "/id"
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},
"source_id": "core-osv",
"document_id": 500225,
"published_at": "2026-08-10T13:45:31.618+00:00"
}