PYSEC-2025-267

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Import Source
https://github.com/pypa/advisory-database/blob/main/vulns/tornado/PYSEC-2025-267.yaml
JSON Data
https://api.osv.dev/v1/vulns/PYSEC-2025-267
Aliases
Published
2025-12-12T07:15:44.920Z
Modified
2026-07-13T07:15:45.375541292Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
[none]
Details

Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an inefficient algorithm when parsing parameters for HTTP header values, potentially causing a DoS. The _parseparam function in httputil.py is used to parse specific HTTP header values, such as those in multipart/form-data and repeatedly calls string.count() within a nested loop while processing quoted semicolons. If an attacker sends a request with a large number of maliciously crafted parameters in a Content-Disposition header, the server's CPU usage increases quadratically (O(n²)) during parsing. Due to Tornado's single event loop architecture, a single malicious request can cause the entire server to become unresponsive for an extended period. This issue is fixed in version 6.5.3.

References

Affected packages

PyPI / tornado

Package

Name
tornado
View open source insights on deps.dev
Purl
pkg:pypi/tornado

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
6.5.3

Affected versions

0.*
0.2
1.*
1.0
1.1
1.1.1
1.2
1.2.1
2.*
2.0
2.1
2.1.1
2.2
2.2.1
2.3
2.4
2.4.1
3.*
3.0
3.0.1
3.0.2
3.1
3.1.1
3.2
3.2.1
3.2.2
4.*
4.0
4.0.1
4.0.2
4.1b2
4.1
4.2b1
4.2
4.2.1
4.3b1
4.3b2
4.3
4.4b1
4.4
4.4.1
4.4.2
4.4.3
4.5b1
4.5b2
4.5
4.5.1
4.5.2
4.5.3
5.*
5.0a1
5.0b1
5.0
5.0.1
5.0.2
5.1b1
5.1
5.1.1
6.*
6.0a1
6.0b1
6.0
6.0.1
6.0.2
6.0.3
6.0.4
6.1b1
6.1b2
6.1
6.2b1
6.2b2
6.2
6.3b1
6.3
6.3.1
6.3.2
6.3.3
6.4b1
6.4
6.4.1
6.4.2
6.5b1
6.5
6.5.1
6.5.2

Database specific

source 
"https://github.com/pypa/advisory-database/blob/main/vulns/tornado/PYSEC-2025-267.yaml"