CVE-2026-49854

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 64% 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
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, the optional native extension tornado.speedups implemented websocket_mask without validating that the mask argument is exactly four bytes, allowing the C function to read up to three bytes beyond the provided buffer when reached through Tornado XSRF token decoding with the native extension active. This issue is fixed in version 6.5.6.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
—
EPSS
36.7%
KEV
Not listed

Published

June 12, 2026

Last Modified

July 15, 2026

Advisory Details (3)

Auto-updated Jul 15, 2026
Patch available. Sources: github_commit, github_pr, github.
github Patch Available

Out-of-bounds memory access in C extension · Advisory · tornadoweb/tornado · GitHub

https://github.com/tornadoweb/tornado/security/advisories/GHSA-cx3h-4qpv-8hc9
github_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/3626
github_commit

commit 96dc88c2a057 (tornadoweb/tornado)

Fix landed in tornadoweb/tornado commit 96dc88c2a057 — awaiting tagged release

https://github.com/tornadoweb/tornado/commit/96dc88c2a05705287856b2cd6b4b4034f9a6aaac

Vendor Advisories for CVE-2026-49854(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)
PackageVulnerable rangeFixed inDependents
tornado0.2 ... 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 9× in last 7d / 12× 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.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:25 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 14:31 UTCEPSS rescore
  6. 2026-07-19 02:29 UTCEPSS rescore
  7. 2026-07-18 10:04 UTCEPSS rescore
  8. 2026-07-17 06:14 UTCEG score recompute▲ 1.60
  9. 2026-07-16 17:03 UTCEPSS rescore
  10. 2026-07-15 16:57 UTCEPSS rescore
  11. 2026-07-15 16:57 UTCEPSS rescore
  12. 2026-07-14 20:50 UTCMITRE cvelistV5CVSS v3 → 5.3 · severity → MEDIUM
  13. 2026-06-14 23:18 UTCEPSS rescore
  14. 2026-06-13 23:00 UTCEPSS rescore
  15. 2026-06-12 23:12 UTCEPSS rescore
  16. 2026-06-12 19:11 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-49854?
CVE-2026-49854 is a medium vulnerability published on June 12, 2026. Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, the optional native extension tornado.speedups implemented websocket_mask without validating that the mask argument is exactly four bytes, allowing the C function to read up to three bytes beyond the provided…
When was CVE-2026-49854 disclosed?
CVE-2026-49854 was first published in the National Vulnerability Database on June 12, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-49854 actively exploited?
CVE-2026-49854 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 36.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-49854?
CVE-2026-49854 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-49854?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-49854, 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

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