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Full vulnerability report · 2025
CVE-2025-67725High confidence

Tornado is Vulnerable to Quadratic DoS via Repeated Header Coalescing

tornadoweb · tornado

Official source article: GitHub GHSA-C98P-7WGM-6P64 ↗. Check the applicable product and release in the original source.

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.56% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs tornadoweb tornado and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Alpine, Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

6 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Alpine v3.23v3.23 · communitypy3-tornadoVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.6.5.4-r0Alpine Security Database ↗Source updated 11 Sep 2026
Debian trixietrixie · sourcepython-tornadoVendor fix publishedDebian records a fixed source-package version for this release.6.4.2-3+deb13u2Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcepython-tornadoVendor fix publishedDebian records a fixed source-package version for this release.6.2.0-3+deb12u4Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcepython-tornadoVendor fix publishedDebian records a fixed source-package version for this release.6.5.4-0.1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcepython-tornadoVendor fix publishedDebian records a fixed source-package version for this release.6.5.4-0.1Debian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivepython-tornadoVendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.6.4.0-1ubuntu0.4Canonical Ubuntu Security ↗Source updated 5 Oct 2026
Open-source package ranges1 source-attributed range

These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.

Ecosystem and packageAffected rangeFirst fixed versionEvidence
piptornado< 6.5.36.5.3GitHub advisory ↗upstream repository advisory · 20 Jul 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2025-67725 · CSAF 2.0 · revision 28 · interimSUSE Product Security TeamCVE-2025-67725
77 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • python-tornado as component of SUSE Linux Enterprise Desktop 15 SP6
  • python-tornado6 as component of SUSE Linux Enterprise Desktop 15 SP6
  • python3-tornado as component of SUSE Linux Enterprise Desktop 15 SP6
  • python311-tornado6 as component of SUSE Linux Enterprise Desktop 15 SP6
  • python-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • python2-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • python3-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • python-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • python2-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • python3-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • python-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS
  • python3-tornado as component of SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS
Summary
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(n^2) 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.
Remediation
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2025-203031

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

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.

What

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.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

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.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Uncontrolled Resource Consumption → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-400 ↗

CWE-400: Uncontrolled Resource Consumption. The product does not properly control the allocation and maintenance of a limited resource.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-400
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-2933Splunk SOAR: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Splunk SOAR ausnutzen, um Sicherheitsvorkehrungen zu umgehen, um Informationen offenzulegen, um Dateien zu manipulieren, um einen SQL-Injection Angriff durchzuführen, um einen Cross-Site Scripting Angriff durchzuführen, und um beliebigen Programmcode auszuführen.

Official advisory ↗
BSI · German · WID-SEC-2026-0195Red Hat Enterprise Linux (pcs / tornado): Mehrere Schwachstellen ermöglichen Denial of Service

Ein Angreifer kann mehrere Schwachstellen in Red Hat Enterprise Linux in pcs bezüglich der tornado Komponente ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1056Multiples vulnérabilités dans les produits Splunk

ecord?id=CVE-2025-14017 Référence CVE CVE-2025-14550 https://www.cve.org/CVERecord?id=CVE-2025-14550 Référence CVE CVE-2025-14819 https://www.cve.org/CVERecord?id=CVE-2025-14819 Référence CVE CVE-2025-15599 https://www.cve.org/CVERecord?id=CVE-2025-15599 Référence CVE CVE-2025-53859 https://www.cve.org/CVERecord?id=CVE-2025-53859 Référence CVE CVE-2025-6545 https://www.cve.org/CVERecord?id=CVE-2025-6545 Référence CVE CVE-2025-6547 https://www.cve.org/CVERecord?id=CVE-2025-6547 Référence CVE CVE-2025-66221 https://www.cve.org/CVERecord?id=CVE-2025-66221 Référence CVE CVE-2025-67724 https://www.cve.org/CVERecord?id=CVE-2025-67724 Référence CVE CVE-2025-67725 https://www.cve.org/CVERecord?id=CVE-2025-67725 Référence CVE CVE-2025-67726 https://www.cve.org/CVERecord?id=CVE-2025-67726 Référence CVE CVE-2025-68428 https://www.cve.org/CVERecord?id=CVE-2025-68428 Référence CVE CVE-2025-69873 https://www.cve.org/CVERecord?id=CVE-2025-69873 Référence CVE CVE-2026-0540 https://www.cve.org/CVERecord?id=CVE-2026-0540 Référence CVE CVE-2026-1207 https://www.cve.org/CVERecord?id=CVE-2026-1207 Référence CVE CVE-2026-1285 https://www.cve.org/CVERecord?id=CVE-2026-1285 Référence CVE CVE-2026-1287 https://www.cve.org/CVERecord?id=CVE-2026-1287 Référence CVE CVE-2026-1312 https://www.cve.org/CVERecord?id=CVE-2026-

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0901Multiples vulnérabilités dans les produits IBM

ord?id=CVE-2025-59437 Référence CVE CVE-2025-59471 https://www.cve.org/CVERecord?id=CVE-2025-59471 Référence CVE CVE-2025-59472 https://www.cve.org/CVERecord?id=CVE-2025-59472 Référence CVE CVE-2025-62718 https://www.cve.org/CVERecord?id=CVE-2025-62718 Référence CVE CVE-2025-6493 https://www.cve.org/CVERecord?id=CVE-2025-6493 Référence CVE CVE-2025-66221 https://www.cve.org/CVERecord?id=CVE-2025-66221 Référence CVE CVE-2025-66418 https://www.cve.org/CVERecord?id=CVE-2025-66418 Référence CVE CVE-2025-66471 https://www.cve.org/CVERecord?id=CVE-2025-66471 Référence CVE CVE-2025-67724 https://www.cve.org/CVERecord?id=CVE-2025-67724 Référence CVE CVE-2025-67725 https://www.cve.org/CVERecord?id=CVE-2025-67725 Référence CVE CVE-2025-67726 https://www.cve.org/CVERecord?id=CVE-2025-67726 Référence CVE CVE-2025-68157 https://www.cve.org/CVERecord?id=CVE-2025-68157 Référence CVE CVE-2025-68458 https://www.cve.org/CVERecord?id=CVE-2025-68458 Référence CVE CVE-2025-68470 https://www.cve.org/CVERecord?id=CVE-2025-68470 Référence CVE CVE-2025-69873 https://www.cve.org/CVERecord?id=CVE-2025-69873 Référence CVE CVE-2025-71176 https://www.cve.org/CVERecord?id=CVE-2025-71176 Référence CVE CVE-2026-0540 https://www.cve.org/CVERecord?id=CVE-2026-0540 Référence CVE CVE-2026-10535 https://www.cve.org/CVERecord?id=CV

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2025-023137tornadoweb の Tornado におけるリソースの枯渇に関する脆弱性

tornadoweb の Tornado には、リソースの枯渇に関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
6.5.3.
Action
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 12 Dec 2025 · Last source change 18 Dec 2025, 18:51 UTC · CWE-400 · Uncontrolled Resource Consumption

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2025-203031
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · SUSE Product Security Team
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2025-203031↗Vendor CSAF · SUSE Product Security Team↗CVE authority or vendor reference · GitHub GHSA-C98P-7WGM-6P64↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2025-67725 · cve.blacktree.nl