Resource Exhaustion Affecting python3-tornado package, versions <4.5.3-150000.3.13.1


Severity

Recommended
0.0
high
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.56% (44th percentile)

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  • Snyk IDSNYK-SLES154-PYTHON3TORNADO-15065095
  • published23 Jan 2026
  • disclosed22 Jan 2026

Introduced: 22 Jan 2026

CVE-2025-67725  (opens in a new tab)
CWE-400  (opens in a new tab)

How to fix?

Upgrade SLES:15.4 python3-tornado to version 4.5.3-150000.3.13.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream python3-tornado package and not the python3-tornado package as distributed by SLES. See How to fix? for SLES:15.4 relevant fixed versions and status.

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 Base Scores

version 3.1