Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, SimpleAsyncHTTPClient shallow-copied redirected requests and removed only the Host header, leaving Authorization, auth_username, auth_password, and auth_mode in place when a redirect changed scheme, host, or port. This issue is fixed in version 6.5.6.
CVE-2026-49853
HIGHPre-NVD 7.77.7—
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 7.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 61% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.7
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.7Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.7
- EG Score
- 7.7(medium)
- EG Risk
- —
- EPSS
- 39.0%
- KEV
- Not listed
Published
June 15, 2026
Last Modified
July 21, 2026
Advisory Details (3)
Auto-updated Jul 15, 2026Patch available. Sources: github, github_commit, github_pr.
github Patch Available
Authorization header forwarded across cross-origin redirects in SimpleAsyncHTTPClient · Advisory · tornadoweb/tornado · GitHub
https://github.com/tornadoweb/tornado/security/advisories/GHSA-3x9g-8vmp-wqvfgithub_pr
Combined changes for release 6.5.6
Fix merged in tornadoweb/tornado PR #3626 on 2026-05-27 — awaiting tagged release
https://github.com/tornadoweb/tornado/pull/3626github_commit
commit aba2569f7ed7 (tornadoweb/tornado)
Fix landed in tornadoweb/tornado commit aba2569f7ed7 — awaiting tagged release
https://github.com/tornadoweb/tornado/commit/aba2569f7ed7a6bdbef816658fb6b7182531b751Vendor Advisories for CVE-2026-49853(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| tornado | 0.2 ... 6.5b1 (81 versions) | 6.5.6 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 8× in last 7d / 10× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-20 17:08 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 02:29 UTCEPSS rescore
- 2026-07-18 10:04 UTCEPSS rescore
- 2026-07-16 17:03 UTCEPSS rescore
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-06-15 20:46 UTCEG score recompute
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-49853?
CVE-2026-49853 is a high vulnerability published on June 15, 2026. Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, SimpleAsyncHTTPClient shallow-copied redirected requests and removed only the Host header, leaving Authorization, authusername, authpassword, and auth_mode in place when a redirect changed scheme, host, or port.…
When was CVE-2026-49853 disclosed?
CVE-2026-49853 was first published in the National Vulnerability Database on June 15, 2026, with the most recent update on July 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-49853 actively exploited?
CVE-2026-49853 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 39.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-49853?
CVE-2026-49853 has a CVSS v3 base score of 7.7 (NVD).
How do I remediate CVE-2026-49853?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-49853, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-49853
Is Your Infrastructure Affected by CVE-2026-49853?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.