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.
CVE-2025-67726
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 89% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EPSS
- 30.0%
- KEV
- Not listed
Published
December 12, 2025
Last Modified
June 17, 2026
References (3)
- security-advisories@githubhttps://github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd
- security-advisories@githubhttps://github.com/tornadoweb/tornado/releases/tag/v6.5.3
- security-advisories@githubhttps://github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8
Vendor Advisories for CVE-2025-67726(7)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:3713Red Hat Product SecurityCritical
Red Hat Security Advisory: RHOAI 3.3 - Red Hat OpenShift AI
- RHSA-2026:2484Red Hat Product SecurityHigh
Red Hat Security Advisory: pcs security update
- RHSA-2026:2469Red Hat Product SecurityHigh
Red Hat Security Advisory: pcs security update
- RHSA-2026:2465Red Hat Product SecurityHigh
Red Hat Security Advisory: pcs security update
- RHSA-2026:2462Red Hat Product SecurityHigh
Red Hat Security Advisory: pcs security update
- RHSA-2026:2106Red Hat Product SecurityHigh
Red Hat Security Advisory: RHOAI 2.25.2 - Red Hat OpenShift AI
- RHSA-2026:0930Red Hat Product SecurityMedium
Red Hat Security Advisory: pcs security update
Patch Availability(8)
| Vendor / Ecosystem | Fixed in / Patch | Released | Source |
|---|---|---|---|
| ubuntu | python3-tornado (4.2.1-1ubuntu3.1+esm2) @ xenial | 2026-05-29 | ubuntu |
| redhat | rhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9:1771874181 | 2026-03-04 | redhat |
| redhat | pcs-0:0.10.15-4.el8_8.10 | 2026-02-10 | redhat |
| redhat | pcs-0:0.11.1-10.el9_0.10 | 2026-02-10 | redhat |
| redhat | pcs-0:0.10.8-1.el8_4.10 | 2026-02-10 | redhat |
| redhat | pcs-0:0.10.12-6.el8_6.12 | 2026-02-10 | redhat |
| redhat | rhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9:1770055425 | 2026-02-05 | redhat |
| redhat | pcs-0:0.10.18-2.el8_10.8 | 2026-01-21 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| tornado | 0.2 ... 6.5b1 (78 versions) | 6.5.3 | — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Additional Vendor Advisories
(1)
Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.
Data Freshness Timeline
(refreshed 9× in last 7d / 45× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-15 01:59 UTCEPSS rescore
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- 2026-07-13 22:29 UTCEPSS rescore
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- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 07:41 UTCOSV refresh
- 2026-07-06 02:23 UTCEPSS rescore
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- 2026-07-05 02:30 UTCEPSS rescore
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- 2026-07-04 06:30 UTCEPSS rescore
- 2026-07-01 15:06 UTCEPSS rescore
- 2026-07-01 15:06 UTCEPSS rescore
- 2026-06-30 23:22 UTCEPSS rescore
- 2026-06-28 14:07 UTCEPSS rescore
- 2026-06-28 14:07 UTCEPSS rescore
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- 2026-06-28 04:56 UTCEPSS rescore
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- 2026-06-21 14:56 UTCEPSS rescore
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- 2026-06-21 01:59 UTCEPSS rescore
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- 2026-06-19 19:25 UTCEPSS rescore
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- 2026-06-18 17:52 UTCEPSS rescore
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- 2026-06-17 19:35 UTCOSV refresh
- 2026-06-17 17:52 UTCEPSS rescore
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- 2026-06-01 13:51 UTCEPSS rescore
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- 2026-05-31 22:30 UTCEPSS rescore
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- 2026-05-31 00:16 UTCEPSS rescore
- 2026-05-31 00:16 UTCEPSS rescore
- 2026-05-29 17:40 UTCEG score recompute
- 2026-05-29 17:40 UTCVendor advisory
- 2026-05-29 13:44 UTCEPSS rescore
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Frequently asked(5)
What is CVE-2025-67726?
When was CVE-2025-67726 disclosed?
Is CVE-2025-67726 actively exploited?
What is the CVSS score of CVE-2025-67726?
How do I remediate CVE-2025-67726?
Dependency Blast Radius
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