tornado AsyncHTTPClient accumulates decompressed chunks without size limit (gzip bomb)
Priority MEDIUM 40CWE-409Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 8 fixed, 6 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00572 47th percentileScored 2026-11-07
Fix Partial tornado (tornadoweb): 6.5.6tornado (PyPI): 6.5.6Red Hat: 8 advisoriesRed Hat: 8 fixed, 6 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| tornadoweb | tornado | before 6.5.6 | 6.5.6 | Patch available | CNA |
| — | tornado (PyPI) | before 6.5.6 | 6.5.6 | Patch available | GHSA-mgf9-4vpg-hj56 |
- tornado Vendortornadoweb Affected before 6.5.6 Fixed in 6.5.6 Patch available CNA
- tornado (PyPI) Vendor— Affected before 6.5.6 Fixed in 6.5.6 Patch available GHSA-mgf9-4vpg-hj56
CPE names Threatist (inferred) · 1
Inferred from how NVD named this product before; not given by a source.
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:* | — | — | tornadoweb |
- cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:* Versions — — ·tornadoweb
Remediation
- Fix · CNA tornado (tornadoweb) Fixed in 6.5.6
- Fix · GHSA-mgf9-4vpg-hj56 tornado (PyPI) Fixed in 6.5.6 Advisory →
Red Hat 8 advisories
- RHSA-2026:90283 Released 2026-10-26 · Red Hat rating Importantpython-tornado security update
- 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
- RHSA-2026:87410 Released 2026-10-21 · Red Hat rating CriticalRHOAI 2.25.12 - Red Hat OpenShift AI
- Red Hat OpenShift AI 2.25 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-caikit-nlp-rhel9, registry.redhat.io/rhoai/odh-codeflare-operator-rhel9 +47
- RHSA-2026:86891 Released 2026-10-21 · Red Hat rating CriticalRHOAI 3.5.2 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.5 registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-cli-rhel9 +47
Show 5 more Red Hat advisories
- RHSA-2026:84734 Released 2026-10-19 · Red Hat rating CriticalRHOAI 3.4.5 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.4 registry.redhat.io/rhoai/odh-ai-gateway-payload-processing-rhel9, registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-autorag-rhel9 +47
- RHSA-2026:80741 Released 2026-10-12 · Red Hat rating Importantpython-tornado security update
- 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
- RHSA-2026:73987 Released 2026-09-30 · Red Hat rating CriticalRHOAI 3.3.7 - Red Hat OpenShift AI
- Red Hat OpenShift AI 3.3 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-dashboard-rhel9, registry.redhat.io/rhoai/odh-data-science-pipelines-argo-argoexec-rhel9 +47
- RHSA-2026:67146 Released 2026-09-14 · Red Hat rating Importantpython-tornado security update
- 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
- RHSA-2026:67147 Released 2026-09-14 · Red Hat rating Importantpython-tornado security update
- 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
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Exploit Intelligence | Affected | No fix planned: Will not fix |
| Red Hat Enterprise Linux 10 | Affected | No fix yet |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
| Red Hat Enterprise Linux AI (RHEL AI) 3 | Affected | No fix yet |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet |
| Red Hat Enterprise Linux AppStream (v. 10) | Fixed | RHSA-2026:67147 |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2026:67146 |
| Red Hat Enterprise Linux AppStream EUS (v. 10.0) | Fixed | RHSA-2026:80741 |
| Red Hat Enterprise Linux AppStream EUS (v.9.6) | Fixed | RHSA-2026:90283 |
| Red Hat OpenShift AI 2.25 | Fixed | RHSA-2026:87410 |
| Red Hat OpenShift AI 3.3 | Fixed | RHSA-2026:73987 |
| Red Hat OpenShift AI 3.4 | Fixed | RHSA-2026:84734 |
| Red Hat OpenShift AI 3.5 | Fixed | RHSA-2026:86891 |
Not affected: 11 products
- Lightspeed Core
- Migration Toolkit for Applications 8
- OpenShift Lightspeed
- Red Hat Ansible Automation Platform 2
- Red Hat Enterprise Linux 8
- Red Hat OpenShift AI 2.25
- Red Hat OpenShift AI 3.3
- Red Hat OpenShift AI 3.4
- Red Hat OpenShift AI 3.5
- Red Hat OpenShift Container Platform 4
- Red Hat OpenStack Platform 16.2
Timeline
- 2026-10-02 Threatist record created from CVE-2026-49855
- 2026-10-03 Alias added: GHSA-mgf9-4vpg-hj56
- 2026-10-07 Fix available: RHSA-2026:73987 · Red Hat
- 2026-10-12 Fix available: RHSA-2026:80741 · Red Hat
- 2026-10-12 Fix available: Red Hat Enterprise Linux AppStream EUS (v. 10.0) · Red Hat
- 2026-10-13 Affected versions changed · Red Hat
- 2026-10-20 Fix available: RHSA-2026:84734 · Red Hat
- 2026-10-20 Fix available: Red Hat OpenShift AI 3.4 · Red Hat
- 2026-10-22 Fix available: RHSA-2026:86891 · Red Hat
- 2026-10-22 Fix available: RHSA-2026:87410 · Red Hat
- 2026-10-23 Fix available: Red Hat OpenShift AI 2.25, Red Hat OpenShift AI 3.5 · Red Hat
- 2026-10-27 Fix available: Red Hat Enterprise Linux AppStream EUS (v.9.6) · Red Hat
- 2026-10-29 Fix available: RHSA-2026:90283 · Red Hat
References
More tornadoweb vulnerabilities
- TI-2026-65637 Tornado before 6.5.9 Denial of Service via CurlAsyncHTTPClient CVSS 4.0HIGH 8.7
- TI-2026-62120 Tornado before 6.5.8 Memory Amplification DoS via multipart CVSS 4.0HIGH 8.7
- TI-2024-13023 Tornado before 6.4.1 HTTP Request Smuggling via Transfer-Encoding CVSS 4.0CRITICAL 9.0
- TI-2026-65638 Tornado before 6.5.9 StaticFileHandler Path Traversal via Symlink CVSS 4.0HIGH 8.2
- TI-2026-62122 Tornado before 6.5.7 Credential Leak via Handle Reuse CVSS 4.0HIGH 8.2
- TI-2026-62121 Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs CVSS 4.0MEDIUM 6.3
Sources
- CVE-2026-49855 · CVE Program
- CVE-2026-49855 · NVD
- FIRST EPSS
- GHSA-mgf9-4vpg-hj56 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-49855 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences