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Fencer Vulns
high 7.5

CVE-2026-49855 json

tornado AsyncHTTPClient accumulates decompressed chunks without size limit (gzip bomb)

published 2026-06-15 4 mo ago modified 2026-10-24 15 d ago also EUVD-2026-44505 , GHSA-mgf9-4vpg-hj56 , PYSEC-2026-3389

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 47%
public exploits
0
none known

Summary

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request=True to consume effectively unlimited memory. This issue is fixed in version 6.5.6.

Patch / fix

  • pypi tornado 6.5.6
  • tornadoweb tornado 6.5.6
  • python-tornado RHEL 10.2 6.5.8-0.el10_2.1
  • python3-tornado RHEL 10.2 6.5.8-0.el10_2.1
  • python-tornado RHEL 9 6.5.8-0.el9_8.1
  • python3-tornado RHEL 9 6.5.8-0.el9_8.1
  • python-tornado enterprise linux eus 10.0 6.5.8-0.el10_0.1
  • python3-tornado enterprise linux eus 10.0 6.5.8-0.el10_0.1

red hat advisories RHSA-2026:80741RHSA-2026:67147RHSA-2026:67146

  • grafana Multi Linux Manager Tools SLE-15 12.4.10-150002.4.27.1
  • mgr-push Multi Linux Manager Tools SLE-15 5.2.5-150002.3.12.1
  • spacecmd Multi Linux Manager Tools SLE-15 5.2.10-150002.3.15.1
  • uyuni-tools Multi Linux Manager Tools SLE-Micro-5, Multi Linux Manager Tools SLE-15 5.2.17-150002.3.20.1
  • venv-salt-minion Multi Linux Manager Tools SLE-Micro-5, Multi Linux Manager Tools SLE-15 3006.0-150002.5.22.1
  • spacewalk-client-tools Multi Linux Manager Tools SLE-15 5.2.7-150002.3.12.1
  • golang-github-prometheus-prometheus Multi Linux Manager Tools SLE-15 3.13.2-150002.3.19.1
  • mgr-push Multi Linux Manager Tools SLE-12 5.2.5-120002.3.12.1

suse advisories SUSE-SU-2026:4585-1SUSE-SU-2026:4584-1SUSE-SU-2026:4583-1SUSE-SU-2026:4582-1SUSE-SU-2026:4581-1SUSE-SU-2026:4580-1

  • python-tornado6 openSUSE Leap 16.0 6.5-160000.5.1
  • python-tornado6 openSUSE Tumbleweed 6.5.7-1.1

opensuse advisories openSUSE-SU-2026:21067-1openSUSE-SU-2026:11027-1

  • python3-tornado AlmaLinux 9 6.5.8-0.el9_8.1
  • python3-tornado AlmaLinux 10 6.5.8-0.el10_2.1

almalinux advisories ALSA-2026:67146ALSA-2026:67147

  • python-tornado Rocky Linux 9 6.5.8-0.el9_8.1
  • python-tornado Rocky Linux 10 6.5.8-0.el10_2.1

rocky linux advisories RLSA-2026:67146RLSA-2026:67147

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-2026-49855 updated cvss 7.5

tornado: Tornado: Denial of Service via uncontrolled gzip decompression memory consumption

  • Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 9 keylime, keylime-base, keylime-tenant, keylime-selinux, python3-keylime, keylime-verifier, +2 more
    affected: workaround, no fix available
  • 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
    affected: workaround, no fix available, no fix planned “Will not fix”
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-th06-cpu-torch291-py312-rhel9, rhoai/odh-th06-cuda130-torch291-py312-rhel9 Red Hat OpenShift Container Platform 4 python-tornado
    affected: workaround, no fix available
  • Red Hat Enterprise Linux AppStream (v. 9) python-tornado 6.5.8-0.el9_8.1, python3-tornado 6.5.8-0.el9_8.1
    fixed: vendor fix RHSA-2026:67146
  • Red Hat Enterprise Linux AppStream (v. 10) python-tornado 6.5.8-0.el10_2.1, python3-tornado 6.5.8-0.el10_2.1
    fixed: vendor fix RHSA-2026:67147
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) python-tornado 6.5.8-0.el10_0.1, python3-tornado 6.5.8-0.el10_0.1
    fixed: vendor fix RHSA-2026:80741
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) python-tornado 6.4.2-2.el9_6.7, python3-tornado 6.4.2-2.el9_6.7
    fixed: vendor fix RHSA-2026:90283
show 10 more
  • Red Hat OpenShift AI 2.25 rhoai/odh-feature-server-rhel9 1792148523, rhoai/odh-llama-stack-core-rhel9 1791873747, rhoai/odh-pipeline-runtime-minimal-cpu-py312-rhel9 1791393968, rhoai/odh-pipeline-runtime-pytorch-cuda-py312-rhel9 1791902759, rhoai/odh-pipeline-runtime-pytorch-rocm-py312-rhel9 1791867137, rhoai/odh-workbench-jupyter-minimal-cpu-py312-rhel9 1791870787, +14 more
    fixed: vendor fix RHSA-2026:87410
  • Red Hat OpenShift AI 3.3 rhoai/odh-llama-stack-core-rhel9 1789121286
    fixed: vendor fix RHSA-2026:73987
  • Red Hat OpenShift AI 3.4 rhoai/odh-feature-server-rhel9 1791863220, rhoai/odh-llama-stack-core-rhel9 1790958470, rhoai/odh-th06-cpu-torch210-py312-rhel9 1791874335, rhoai/odh-th06-rocm64-torch291-py312-rhel9 1791872119, rhoai/odh-th06-cuda130-torch210-py312-rhel9 1791961113, rhoai/odh-trustyai-nemo-guardrails-server-rhel9 1791556128
    fixed: vendor fix RHSA-2026:84734
  • Red Hat OpenShift AI 3.5 rhoai/odh-trustyai-nemo-guardrails-server-rhel9 1791566631, rhoai/odh-pipeline-runtime-minimal-cpu-py312-rhel9 1791572004, rhoai/odh-pipeline-runtime-pytorch-cuda-py312-rhel9 1791816462, rhoai/odh-pipeline-runtime-pytorch-rocm-py312-rhel9 1791951049, rhoai/odh-workbench-jupyter-minimal-cpu-py312-rhel9 1791572098, rhoai/odh-workbench-jupyter-minimal-cuda-py312-rhel9 1791572144, +13 more
    fixed: vendor fix RHSA-2026:86891
  • Red Hat Lightspeed Core lightspeed-core/rag-tool-cpu-rhel9, lightspeed-core/lightspeed-stack-rhel9, lightspeed-core/rag-tool-cuda-12.9-rhel9
    not affected: vulnerable code not present
  • Red Hat Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9
    not affected: component not present
  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/lightspeed-chatbot-rhel9, ansible-automation-platform-27/lightspeed-chatbot-rhel9
    not affected: vulnerable code not present
  • Red Hat Enterprise Linux 8 pcs, pcs-snmp
    not affected: vulnerable code not in execute path
  • Red Hat Enterprise Linux 10 keylime 7.14.1-5.el10_2.1
    not affected: component not present
  • Red Hat OpenShift AI 2.25 rhoai/odh-rhel9-operator 1792570619, rhoai/odh-vllm-cpu-rhel9 1792018436, rhoai/odh-dashboard-rhel9 1791853525, rhoai/odh-modelmesh-rhel9 1790881700, rhoai/odh-operator-bundle 1792571069, rhoai/odh-vllm-cuda-rhel9 1791358976, +46 more Red Hat OpenShift AI 3.3 rhoai/odh-cli-rhel9 1790070206, rhoai/rhai-cli-rhel9 1790070206, rhoai/odh-mlflow-rhel9 1789653606, rhoai/odh-trainer-rhel9 1790136369, rhoai/odh-maas-api-rhel9 1790131842, rhoai/odh-mlserver-rhel9 1789121365, +76 more Red Hat OpenShift AI 3.4 rhoai/odh-cli-rhel9 1791509689, rhoai/rhai-cli-rhel9 1791509689, rhoai/odh-automl-rhel9 1791535789, rhoai/odh-mlflow-rhel9 1791865967, rhoai/odh-autorag-rhel9 1791557539, rhoai/odh-trainer-rhel9 1791869783, +94 more Red Hat OpenShift AI 3.5 rhoai/odh-cli-rhel9 1791945905, rhoai/rhai-cli-rhel9 1791945905, rhoai/odh-automl-rhel9 1791916705, rhoai/odh-mlflow-rhel9 1791947857, rhoai/odh-autorag-rhel9 1791903266, rhoai/odh-trainer-rhel9 1791952138, +94 more Red Hat OpenShift Container Platform 4 python-pep517 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
    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
none
Automatable
yes
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.57% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi tornado
<6.5.6
6.5.6

Affected products

  • tornadoweb tornado

Classification

Weakness
  • CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)

References

Sources

Fencer Vulns 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.

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