CVE catalog
CVE-2026-103261
Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query
- Severity
- Medium · CVSS 6.9
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Published
- Updated
- Source
- [NVD] · [CVE record]
- EPSS
- 0.47% · Oct 25, 2026
Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | python-tornado | sid | 6.5.5-5 | vulnerable |
| Debian | python-tornado | forky | 6.5.5-5 | vulnerable |
| Debian | python-tornado | trixie | 6.4.2-3+deb13u2 | vulnerable |
| Debian | python-tornado | trixie-security | 6.4.2-3+deb13u2 | vulnerable |
| Debian | python-tornado | bookworm | 6.2.0-3+deb12u4 | vulnerable |
| Debian | python-tornado | bookworm-security | 6.2.0-3+deb12u4 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-1build1 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-2 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-3 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-3build1 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-3ubuntu0.1~esm1 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-3ubuntu0.1~esm2 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-3ubuntu0.1~esm4 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-3ubuntu0.1~esm5 | vulnerable |
| Ubuntu | python-tornado | pro | 6.1.0-3ubuntu0.1~esm6 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.3.2-1 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-0ubuntu1 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-1 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-1build1 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-1ubuntu0.1 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-1ubuntu0.2 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-1ubuntu0.4 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-1ubuntu0.5 | vulnerable |
| Ubuntu | python-tornado | 24.04 | 6.4.0-1ubuntu0.6 | vulnerable |
| Ubuntu | python-tornado | 26.10 | 6.5.4-0.1 | vulnerable |
| Ubuntu | python-tornado | 26.10 | 6.5.5-2 | vulnerable |
| Ubuntu | python-tornado | 26.10 | 6.5.5-4 | vulnerable |
| Ubuntu | python-tornado | 26.10 | 6.5.5-5 | vulnerable |
| Ubuntu | python-tornado | 26.10 | 6.5.5-5ubuntu1.1 | vulnerable |
| Ubuntu | python-tornado | 26.04 | 6.4.2-3 | vulnerable |
| Ubuntu | python-tornado | 26.04 | 6.5.2-3 | vulnerable |
| Ubuntu | python-tornado | 26.04 | 6.5.4-0.1 | vulnerable |
| Ubuntu | python-tornado | 26.04 | 6.5.4-0.1ubuntu0.1 | vulnerable |
| Ubuntu | python-tornado | 26.04 | 6.5.4-0.1ubuntu0.2 | vulnerable |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | python-tornado | source | sid | (unfixed) | not yet assigned | Not reported | [1149712] |
| Debian | python-tornado | source | forky | (unfixed) | not yet assigned | Not reported | [1149712] |
| Debian | python-tornado | source | trixie | (unfixed) | not yet assigned | Not reported | [1149712] |
| Debian | python-tornado | source | bookworm | (unfixed) | not yet assigned | Not reported | [1149712] |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [python3-tornado]Affected
Source package: [python-tornado]
Details (4)
6.2.0-3+deb12u4· amd64 · bookwormAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
6.2.0-3+deb12u4· arm64 · bookwormAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
6.2.0-3+deb12u4· amd64 · bookworm-securityAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
6.2.0-3+deb12u4· arm64 · bookworm-securityAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
- [python-tornado-doc]Affected
Source package: [python-tornado]
Details (4)
6.2.0-3+deb12u4· all · bookwormAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
6.2.0-3+deb12u4· all · bookwormAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
6.2.0-3+deb12u4· all · bookworm-securityAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
6.2.0-3+deb12u4· all · bookworm-securityAffected
nvd · python-tornado · debian · bookworm; nvd · python-tornado · debian · 12
[Debian 13 (Trixie)]
- [python3-tornado]Affected
Source package: [python-tornado]
Details (4)
6.4.2-3+deb13u2· amd64 · trixieAffected
nvd · python-tornado · debian · 13
6.4.2-3+deb13u2· arm64 · trixieAffected
nvd · python-tornado · debian · 13
6.4.2-3+deb13u2· amd64 · trixie-securityAffected
nvd · python-tornado · debian · 13
6.4.2-3+deb13u2· arm64 · trixie-securityAffected
nvd · python-tornado · debian · 13
- [python-tornado-doc]Affected
Source package: [python-tornado]
Details (4)
6.4.2-3+deb13u2· all · trixieAffected
nvd · python-tornado · debian · 13
6.4.2-3+deb13u2· all · trixieAffected
nvd · python-tornado · debian · 13
6.4.2-3+deb13u2· all · trixie-securityAffected
nvd · python-tornado · debian · 13
6.4.2-3+deb13u2· all · trixie-securityAffected
nvd · python-tornado · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-103261]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-103261]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2026-103261]
- [https://security-tracker.debian.org/tracker/CVE-2026-103261]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-103261.json]
[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]