CVE-2026-49854

LOWPre-NVD 3.73.7
EchelonGraph scoreLOW confidence

This low-severity CVE scores 3.7 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit probability: 0.0%, top 92% 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: cna:github_m, epss
3.7
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 3.7Exploit: NoneExposed: 0

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

Tornado has out-of-bounds memory access via C extension

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).

CVSS v3
3.7
EG Score
3.7(low)
EPSS
8.2%
KEV
Not listed

Published

June 12, 2026

Last Modified

June 12, 2026

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—

Data Freshness Timeline

(refreshed 2× in last 7d / 11× 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. 2026-07-04 10:53 UTCEG score recompute
  2. 2026-07-01 02:47 UTCEG score recompute
  3. 2026-06-28 01:46 UTCEG score recompute
  4. 2026-06-25 00:45 UTCEG score recompute
  5. 2026-06-21 23:43 UTCEG score recompute
  6. 2026-06-18 21:16 UTCEG score recompute
  7. 2026-06-15 20:15 UTCEG score recompute
  8. 2026-06-14 23:18 UTCEPSS rescore
  9. 2026-06-13 23:00 UTCEPSS rescore
  10. 2026-06-12 23:12 UTCEPSS rescore
  11. 2026-06-12 19:11 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-49854?
CVE-2026-49854 is a low vulnerability published on June 12, 2026. Tornado has out-of-bounds memory access via C extension 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…
When was CVE-2026-49854 disclosed?
CVE-2026-49854 was first published in the National Vulnerability Database on June 12, 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 8.2% 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 v4.0 base score of 3.7 (CNA self-assessment; NVD's own analysis pending). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
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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