CVE-2026-18503
A vulnerability has been discovered in CPython. It allows an attacker to cause remote denial of service.
CSIRTS triage
- What
- A remote denial-of-service vulnerability has been discovered in CPython.
- Who is affected
- Systems running CPython that accept remote input triggering the DoS condition.
- Urgency
- Unknown severity without CVSS or exploitation details; DoS impact is typically lower priority than RCE.
- Action
- Apply CPython security updates when released and identify affected versions in your environment.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all EPSS-scored CVEs.
Advisory coverage (3)
- unknownCVE-2026-18503: Super-linear CPU usage for unbounded input to csv.Sniffer.sniff()msrc · 2026-08-11
- unknownVulnerability in CPython (August 11, 2026)cert-fr-avis · 2026-08-11
- unknownCVE-2026-18503: Attacker-controlled CSV samples can trigger super-linear regular-expression work during dialec…nvd · 2026-08-10
External references
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[](https://www.csirts.com/cve/CVE-2026-18503)