How severe is CVE-2025-67725?

CVE-2025-67725 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2025-67725 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (32nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-67725?

CVE-2025-67725 affects Tornadoweb Tornado. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-67725?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2025-67725 have an EU (EUVD) identifier?

Yes. CVE-2025-67725 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-203031.

When was CVE-2025-67725 published?

CVE-2025-67725 was published on 2025-12-12 and last updated on 2026-06-17.

CVE-2025-67725

CVE-2025-67725 is a high-severity vulnerability in Tornadoweb Tornado with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (32nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-203031
Weakness: CWE-400
Affected product: Tornadoweb Tornado
Published: 2025-12-12
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2025-67725?: 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.
How severe is CVE-2025-67725?: CVE-2025-67725 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-67725 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (32nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-67725?: CVE-2025-67725 affects Tornadoweb Tornado. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-67725?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2025-67725 have an EU (EUVD) identifier?: Yes. CVE-2025-67725 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-203031.
When was CVE-2025-67725 published?: CVE-2025-67725 was published on 2025-12-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:*

More vulnerabilities in Tornadoweb Tornado

CVE-2026-31958 — High (CVSS 7.5): Tornado is a Python web framework and asynchronous networking library. In versions of Tornado prior to 6.5.5, the only…
CVE-2025-67726 — High (CVSS 7.5): Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an inefficient…
CVE-2025-47287 — High (CVSS 7.5): Tornado is a Python web framework and asynchronous networking library. When Tornado's ``multipart/form-data`` parser…
CVE-2024-52804 — High (CVSS 7.5): Tornado is a Python web framework and asynchronous networking library. The algorithm used for parsing HTTP cookies in…
CVE-2026-35536 — High (CVSS 7.2): In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite arguments to…
CVE-2014-9720 — Medium (CVSS 6.5): Tornado before 3.2.2 sends arbitrary responses that contain a fixed CSRF token and may be sent with HTTP compression,…

All CVEs affecting Tornadoweb Tornado →

Other CWE-400 (Uncontrolled Resource Consumption) vulnerabilities

CVE-2026-46775 — Critical (CVSS 9.9): Vulnerability in Oracle REST Data Services (component: Core). Supported versions that are affected are 24.2.0-26.1.0.…
CVE-2025-61303 — Critical (CVSS 9.8): Hatching Triage Sandbox Windows 10 build 2004 (2025-08-14) and Windows 10 LTSC 2021(2025-08-14) contains a…
CVE-2025-43193 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in macOS Sequoia 15.6, macOS Sonoma 14.7.7,…
CVE-2025-24269 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in macOS Sequoia 15.4. An app may be able to…
CVE-2025-24264 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in Safari 18.4, iOS 18.4 and iPadOS 18.4,…
CVE-2025-24260 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in macOS Sequoia 15.4, macOS Sonoma 14.7.5,…

Browse all CWE-400 (Uncontrolled Resource Consumption) vulnerabilities →