CVE-2026-91990

Public on 2026-09-15

Modified on 2026-09-16

Description

Tornado before 6.5.8 contains a memory amplification vulnerability in parse_multipart_form_data that splits multipart data before validating the max_parts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of service.

Severity

Important

See what this means

CVSS v3 Base Score

7.5

See breakdown

Affected Packages

Platform	Package	Release Date	Advisory	Status
Amazon Linux 2 - Core	python-tornado	2026-10-12	ALAS2-2026-3976	Fixed
Amazon Linux 2023	python-tornado	2026-10-12	ALAS2023-2026-3177	Fixed
Amazon Linux 2027 Preview	python-tornado	2026-10-12	ALAS2027-2026-183	Fixed
Amazon Linux 2 - Core	python3-tornado	2026-10-12	ALAS2-2026-3975	Fixed
Amazon Linux 2023	python3.13-tornado	2026-10-12	ALAS2023-2026-3176	Fixed

CVSS Scores

	Score Type	Score	Vector
Amazon Linux	CVSSv3	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

FAQs regarding Amazon Linux ALAS/CVE Severity Red Hat: CVE-2026-91990 Mitre: CVE-2026-91990