Vulnerability in tornado (CVE-2026-49854)
Summary
Vulnerability in tornado (CVE-2026-49854). Risk of unauthorized operations or information disclosure. Exploitable via tornado.speedups. Mitigation: upgrade to 6.5.6 or later.
Original description
The description as published by the source.
Summary
Tornado's optional native extension tornado.speedups implements websocket_mask without validating that the mask argument is exactly four bytes long. The C function reads four bytes from mask unconditionally, even when Python passes a shorter byte string. This can read beyond the provided buffer, exposing up to 3 bytes of uninitialized memory.
The behavior is reachable from Tornado's XSRF token decoder when xsrf_cookies=True and the native extension is active.
Mitigations
This bug is fixed in Tornado 6.5.6. Prior to upgrading to this version, setting the environment variable TORNADO_EXTENSION=0 will disable the vulnerable code (at the expense of reducing websocket performance).
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-49854 has been found in tornado.
Attackers can target a specific entry point like tornado.speedups over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade tornado to 6.5.6 or later.
If unsure, ask your IT team or search "tornado CVE-2026-49854" on the vendor's site.
CVE-2026-49854 (tornado) — CWE-126 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: tornado.speedups / websocket_mask / mask
Patched: 6.5.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-126) exists in tornado. Attackers reach the vulnerable code path via tornado.speedups without authentication.
Check the vendor advisory for the affected versions of tornado. Attack surface: tornado.speedups / websocket_mask / mask.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 6.5.6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'tornado' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'tornado' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
tornadoを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade tornado to 6.5.6ステージング環境で 6.5.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-49854 python-tornado