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Vulnerabilities

Vulnerability · CVE-2025-67725

Tornado is a Python web framework and asynchronous networking library.

Published Dec 12, 2025 · catalog updated Dec 18, 2025 · Tornado

Last checked Oct 27, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2025-67725. EPSS is 0.56%. Act only if a listed version of Tornado is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.56%
Remediation
Version ranges on file
Affected products
vendor tornadoweb Tornado < 6.5.3

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 defa

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor tornadoweb Tornado < 6.5.3< 6.5.3

How to fix CVE-2025-67725

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-67725. EPSS is 0.56%. Act only if a listed version of Tornado is installed.

Which versions are affected?

Compare what you have installed with tornadoweb Tornado < 6.5.3 < 6.5.3. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.56%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Dec 12, 2025 · EUVD

    Detected

    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 immutabi

  2. Dec 18, 2025 · EUVD

    Updated

    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 immutabi

Sources

  • CVE.orgVulnerability recordCVE-2025-67725

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-67725

    30-day exploitation probability 0.56%

    first.org
  • EUVDVulnerability recordEUVD-2025-203031

    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 stri

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 27, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgOct 27, 2026
  • FIRST EPSSOct 27, 2026
  • EUVDOct 27, 2026