SB2026091516 - Multiple vulnerabilities in Tornado

Description

This security bulletin contains information about 2 vulnerabilities.

1) Resource exhaustion (CVE-ID: N/A)

CWE-ID: CWE-400 - Resource exhaustion

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to uncontrolled resource consumption in the parse_multipart_form_data function in httputil.py when processing multipart/form-data requests. A remote attacker can send a multipart request containing numerous parts to cause a denial of service.

2) Improper Validation of Specified Quantity in Input (CVE-ID: CVE-2026-82397)

CWE-ID: CWE-1284 - Improper Validation of Specified Quantity in Input

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to improper validation of the number of fields in application/x-www-form-urlencoded body parsing when processing a crafted form request containing numerous separators. A remote attacker can send a specially crafted form request to cause a denial of service.

The synchronous parsing occurs on the event loop before request dispatch, causing other connections to wait.

Remediation

Install update from vendor's website.

References

• https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq
• https://github.com/tornadoweb/tornado/security/advisories/GHSA-mpf4-983q-p7j4