CVE-2026-18503: Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()
CSIRTS triage
- What
- The csv.Sniffer.sniff() function exhibits super-linear CPU usage when processing unbounded input, causing denial of service.
- Who is affected
- Applications using Python's csv.Sniffer.sniff() method to parse untrusted or very large CSV data.
- Urgency
- Moderate; exploitation requires attacker control over input, but can exhaust resources and deny service.
- Action
- Update Python to a patched version; validate and limit input size before calling sniff().
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-18503
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-185030.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-18503 | coverage & exploitation status | NVD · CVE.org |
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