CVE-2026-49855

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.7%, top 51% 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
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: 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, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an HTTPServer configured with decompress_request=True to consume effectively unlimited memory. This issue is fixed in version 6.5.6.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
—
EPSS
49.0%
KEV
Not listed

Published

June 15, 2026

Last Modified

July 16, 2026

Advisory Details (3)

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

tornado AsyncHTTPClient accumulates decompressed chunks without size limit (gzip bomb) · Advisory · tornadoweb/tornado · GitHub

https://github.com/tornadoweb/tornado/security/advisories/GHSA-mgf9-4vpg-hj56
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 ff808b33adc5 (tornadoweb/tornado)

Fix landed in tornadoweb/tornado commit ff808b33adc5 — awaiting tagged release

https://github.com/tornadoweb/tornado/commit/ff808b33adc52d89a549376a5e3628e92abbc8ff

Vendor Advisories for CVE-2026-49855(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 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.

  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. 2026-07-16 17:03 UTCEPSS rescore
  9. 2026-07-15 16:57 UTCEPSS rescore
  10. 2026-07-15 16:57 UTCEPSS rescore
  11. 2026-06-15 20:46 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-49855?
CVE-2026-49855 is a high vulnerability published on June 15, 2026. Tornado is a Python web framework and asynchronous networking library. Prior to 6.5.6, Tornado gzip decompression routines processed limited-size chunks but did not enforce an overall limit on accumulated decompressed chunks, allowing a malicious server accessed by SimpleAsyncHTTPClient or an…
When was CVE-2026-49855 disclosed?
CVE-2026-49855 was first published in the National Vulnerability Database on June 15, 2026, with the most recent update on July 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-49855 actively exploited?
CVE-2026-49855 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 49.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-49855?
CVE-2026-49855 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-49855?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-49855, 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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