Vulnerability in Tornado (CVE-2026-103263)
Summary
Vulnerability in Tornado (CVE-2026-103263). Confidential information can be exposed externally.
Original description
The description as published by the source.
Summary
StaticFileHandler allows an unauthenticated attacker to read arbitrary files from the server's filesystem by requesting a path that resolves to a symbolic link placed inside the static root directory. Any application that serves user-uploadable content, or whose static directory is populated by a build/deploy pipeline that creates symlinks (e.g. npm link, webpack, Docker volume mounts, CDN sync tools), is affected. An attacker who can trigger the creation of a symlink pointing outside the static root—or exploit one that already exists—can retrieve sensitive files such as /etc/passwd, private keys, configuration files, or application secrets.
Details
The vulnerability is in tornado.web.StaticFileHandler, specifically in the interaction between two methods in tornado/web.py:
- get_absolute_path uses
os.path.abspath()to resolve the requested path: - validate_absolute_path uses the same
os.path.abspath()on the root, then performs a string prefix check:
os.path.abspath() normalises . and .. segments but does not resolve symbolic links. As a result, a path like /var/www/static/link passes the startswith("/var/www/static/") check regardless of where `link…
Source: NIST National Vulnerability Database 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-2026-103263 has been found in Tornado.
Confidential information can be exposed externally. CVSS score: 5.9/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Tornado CVE-2026-103263" on the vendor's site.
CVE-2026-103263 (Tornado) — CWE-59 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
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-59) exists in Tornado.
Check the vendor advisory for the affected versions of Tornado.
Severity: Medium (CVSS 5.9/10). Confidential information can be exposed externally.
Update to the patched release per vendor advisory.
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
-
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。 -
2Post-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
- Debian DEBIAN-CVE-2026-103263 python-tornado
- Ubuntu UBUNTU-CVE-2026-103263 python-tornado
References
- package github.com
- web github.com
- web github.com
- web vulncheck.com
- web nvd.nist.gov
- web github.com
- web github.com
- web github.com
- web github.com