DEBIAN-CVE-2025-67725

Advisory lineage Upstream: 1 Downstream: 0
Upstream
CVE-2025-67725
Published: 12 Dec 2025, 06:15
Last modified:28 Apr 2026, 20:30

Vulnerability Summary

Overall Risk (default)
medium
30/100
CVSS Score
7.5 HIGH
3.1 (osv_debian)
EPSS Score
No data
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

12 Dec 2025, 06:15
Published
Vulnerability first disclosed
28 Apr 2026, 20:30
Last Modified
Vulnerability information updated

Description

Tornado is a Python web framework and asynchronous networking library. In versions 6.5.2 and below, a single maliciously crafted HTTP request can block the server's event loop for an extended period, caused by the HTTPHeaders.add method. The function accumulates values using string concatenation when the same header name is repeated, causing a Denial of Service (DoS). Due to Python string immutability, each concatenation copies the entire string, resulting in O(n²) time complexity. The severity can vary from high if max_header_size has been increased from its default, to low if it has its default value of 64KB. This issue is fixed in version 6.5.3.

CVSS Metrics

  • v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Systems

  • debian•python-tornado

    all | all | < 6.1.0-1+deb11u3 | < 6.2.0-3+deb12u4 | < 6.4.2-3+deb13u2 | < 6.5.4-0.1

References (1)