Low [CVE-2026-18503] Denial of Service via super-linear regular expression work in csv.Sniffer.sniff
This low-severity Red Hat Linux advisory covers CVE-2026-18503 affecting Red Hat Hardened Images, Exploit Intelligence, Red Hat Enterprise Linux 10.
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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().
A flaw was found in the `csv. This excessive processing consumes significant CPU resources, potentially leading to a Denial of Service (DoS) for applications that process unbounded input using this function.
Red Hat has evaluated this issue and determined it has a Low security impact. Most applications are not affected as they use csv.reader() or csv.
DictReader() directly without invoking the sniffing functionality. Red Hat severity: Low — CVSS 2.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:L).
Weakness: CWE-1333.
Affected Red Hat products: Red Hat Hardened Images; Exploit Intelligence; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat Enterprise Linux AI (RHEL AI) 3; Red Hat Enterprise Linux command line assistant; Red Hat OpenShift AI (RHOAI); Red Hat OpenShift Dev Spaces; Red Hat OpenShift Virtualization 4; Self-service automation portal 2.
Red Hat fixing advisory: RHSA-2026:54534, RHSA-2026:54554, RHSA-2026:57010, RHSA-2026:57660, RHSA-2026:58420.
Affected products named by the advisory: Red Hat package: python3.12; Red Hat package: python36; Red Hat package: python3.9.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 18 days ago·verify at source
- python3-14-main-3.14.7-1.hum1
- python3-13-main-3.13.15-1.hum1
- python3-10-main-3.10.21-1.hum1
- python3-11-main-3.11.16-1.hum1
- python3-12-main-3.12.14-1.hum1
- RHSA-2026:54534
- RHSA-2026:54554
- RHSA-2026:57010
- RHSA-2026:57660
- RHSA-2026:58420
Official advisory · high-confidence parse· fetched 18 days ago·verify at source
Mitigation checklist
- Do not pass untrusted or unbounded CSV input to csv.Sniffer.sniff(). If dialect detection is needed, limit the size of the sample passed to sniff() or use a known dialect directly with csv.reader().
Official advisory · high-confidence parse· fetched 18 days ago·verify at source
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