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Vulnerability · Published Oct 1, 2026 · Assigned by VulnCheck

CVE-2026-103262Tornado before 6.5.9 Denial of Service via CurlAsyncHTTPClient

High 7.5

In plain English

A high-severity security flaw in tornado from tornadoweb. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.6%top 49.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

Tornado versions before 6.5.9 contain an unbounded memory accumulation vulnerability in CurlAsyncHTTPClient that allows remote attackers to cause denial of service by sending a compressed response. Attackers can send a gzip-encoded decompression bomb that accumulates in memory without size limits, causing the application process to be killed by out-of-memory conditions.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10python3-tornado6.5.10-1.el10_2.1ALSA-2026:82041
AlmaLinux:9python3-tornado6.5.10-1.el9_8.1ALSA-2026:82040
Debian:12python-tornadono fix listedDEBIAN-CVE-2026-103262
Debian:13python-tornadono fix listedDEBIAN-CVE-2026-103262
Debian:14python-tornadono fix listedDEBIAN-CVE-2026-103262
PyPItornado6.5.9GHSA-chx6-46f5-w4vp
Rocky Linux:10python-tornado0:6.5.10-1.el10_2.1RLSA-2026:82041
Rocky Linux:9python-tornado0:6.5.10-1.el9_8.1RLSA-2026:82040
Ubuntu:24.04:LTSpython-tornado6.4.0-1ubuntu0.6USN-8952-1
Ubuntu:24.04:LTSpython-tornado6.4.0-1ubuntu0.6UBUNTU-CVE-2026-103262
Ubuntu:26.04:LTSpython-tornado6.5.4-0.1ubuntu0.2UBUNTU-CVE-2026-103262
Ubuntu:26.04:LTSpython-tornado6.5.4-0.1ubuntu0.2USN-8952-1
Ubuntu:26.10python-tornado6.5.5-5ubuntu1.1USN-8952-1

Affected products (as reported)

VendorProductVersions
tornadoweb tornado 0 – before 6.5.9

Weakness: CWE-409 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References