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Fencer Intel
medium 5.4

CVE-2026-91991 json

Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs

published 3mo ago modified last mo. also EUVD-2026-78663 , GHSA-wwv5-g3v4-889x

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

Tornado before 6.5.8 contains an incomplete fix for cookie attribute injection that allows attackers to inject arbitrary cookie attributes by passing capitalized or legacy keyword arguments to set_cookie. Attackers can embed semicolon-delimited data in capitalized parameters like Domain, Path, or SameSite to bypass validation and modify cookie security attributes.

Patch / fix

  • pypi tornado 6.5.8
  • tornadoweb tornado 6.5.8
  • python-tornado6 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.5-160000.7.1
  • python-tornado SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 4.5.3-150000.3.31.1
  • python-tornado6 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 6.3.2-150400.9.27.1

suse advisories SUSE-SU-2026:24121-1SUSE-SU-2026:24207-1SUSE-SU-2026:4404-1SUSE-SU-2026:4403-1

  • python-tornado6 openSUSE Leap 16.0 6.5-160000.7.1

opensuse advisories openSUSE-SU-2026:22059-1

Is CVE-2026-91991 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-91991 updated cvss 5.4

tornado: Tornado: Cookie attribute injection via capitalized keyword arguments

  • Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9
    affected: no fix planned “Out of support scope”
  • Red Hat Lightspeed Core lightspeed-core/rag-tool-cpu-rhel9, lightspeed-core/lightspeed-stack-rhel9, lightspeed-core/rag-tool-cuda-12.9-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9 Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/lightspeed-chatbot-rhel9 Red Hat OpenShift AI (RHOAI) rhoai/odh-feature-server-rhel9, rhoai/odh-llama-stack-core-rhel9, rhoai/odh-th-torch-cpu-py312-rhel9, rhoai/odh-th-torch-cuda-py312-rhel9, rhoai/odh-th-torch-rocm-py312-rhel9, rhoai/odh-th06-cpu-torch210-py312-rhel9, +23 more Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9, python-flit 3.9.0-3.1.el9ocp, python-pep517 0.13.0-5.2.el9ocp, python-tornado 6.5.8-0.el10_2.1 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: no fix available “Fix deferred”
  • Red Hat Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9 Red Hat Ansible Automation Platform 2 ansible-automation-platform-27/lightspeed-chatbot-rhel9 Red Hat Enterprise Linux 8 pcs, pcs-snmp Red Hat Enterprise Linux 9 python3-tornado, rhel9/keylime-verifier, rhel9/keylime-registrar, python-tornado 6.5.8-0.el10_2.1 Red Hat Enterprise Linux 10 rhel10/keylime-verifier, rhel10/keylime-registrar, python-tornado 6.5.8-0.el10_2.1 Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/disk-image-cuda-rhel9
    +2 more products
    Red Hat OpenStack Platform 16.2 rhosp-rhel8/openstack-redis, rhosp-rhel8/openstack-haproxy, rhosp-rhel8/openstack-mariadb, rhosp-rhel8/openstack-rabbitmq, rhosp-rhel8/openstack-ovn-northd, rhosp-rhel8/openstack-manila-share, +2 more Red Hat OpenStack Platform 17.1 rhosp-rhel9/openstack-redis, rhosp-rhel9/openstack-haproxy, rhosp-rhel9/openstack-mariadb, rhosp-rhel9/openstack-rabbitmq, rhosp-rhel9/openstack-ovn-northd, rhosp-rhel9/openstack-manila-share, +2 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/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

Affected packages

ecosystem package affected fixed in
pypi tornado
>=6.5.5, <6.5.8
6.5.8

Affected products

  • tornadoweb tornado

Classification

Weakness
  • CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers
  • CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of tornadoweb/tornado published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.