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HIGH severity

CVE-2026-103262 — Tornadoweb

HIGHFix: tornadoweb/tornado@e412435

CVE-2026-103262 is a high-severity (CVSS 7.5) CWE-409 vulnerability. No vendor fix is recorded yet; mitigation options are listed below.

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…

Published
Oct 1, 2026
Updated
Oct 1, 2026
Affected
—
Patched
See advisory
Exploits
None indexed
Exploitation data as of Oct 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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.

Detection & mitigation playbook

Vulnerability
  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    No fixed release is recorded for CVE-2026-103262 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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CVE-2026-103262: Tornadoweb (High 7.5) | O3 Security