Information Disclosure in tornado (CVE-2026-49853)
Summary
Vulnerability in tornado (CVE-2026-49853). Confidential information can be exposed externally. Exploitable via Host header. Mitigation: upgrade to 6.5.6 or later.
Original description
The description as published by the source.
Summary
When SimpleAsyncHTTPClient follows a 3xx redirect, it shallow-copies the original HTTPRequest, rewrites the URL, decrements max_redirects, and removes only the Host header. It does not clear Authorization, auth_username, auth_password, or auth_mode when the redirect target changes origin.
As a result, credentials intended for one origin can be forwarded to a different origin when follow_redirects=True, which is the default.
Beginning in Tornado 6.5.6, SimpleAsyncHTTPClient matches the default behavior of libcurl (and therefore CurlAsyncHTTPClient): When a redirect changes the scheme, host, or port of the url, the Authorization and Cookie headers will be removed when following the redirect.
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-2026-49853 has been found in tornado.
Attackers can target a specific entry point like Host header over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.7/10.
What to do: upgrade tornado to 6.5.6 or later.
If unsure, ask your IT team or search "tornado CVE-2026-49853" on the vendor's site.
CVE-2026-49853 (tornado) — CWE-200 / CVSS v3 7.7
Attack vector: remote (network-reachable) / no user interaction
Attack surface: Host header / SimpleAsyncHTTPClient / libcurl / CurlAsyncHTTPClient
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.
Information disclosure (CWE-200) exists in tornado. Attackers reach the vulnerable code path via Host header.
Check the vendor advisory for the affected versions of tornado. Attack surface: Host header / SimpleAsyncHTTPClient / libcurl / CurlAsyncHTTPClient.
Severity: High (CVSS 7.7/10). Confidential information can be exposed externally.
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-2026-49853 python-tornado