CVE-2026-91990

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-15. a secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this weekElevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: Elevated riskExposed: 0

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

Tornado before 6.5.8 contains a memory amplification vulnerability in parse_multipart_form_data that splits multipart data before validating the max_parts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of service.

CVSS v3
7.5
EG Score
7.5(high)
EG Risk
65(Attend)
EG Risk 65/100SSVC: Attend

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
0%
EPSS %ILE
35%
KEV
Not listed

Published

September 15, 2026

Last Modified

September 16, 2026

Advisory Details (2)

Auto-updated Sep 15, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

Tornado before 6.5.8 Memory Amplification DoS via multipart | Advisories | VulnCheck

https://www.vulncheck.com/advisories/tornado-before-6.5.8-memory-amplification-dos-via-multipart
github Patch Available🟡 PoC Available

tornado: multipart split() creates huge temp list before max_parts check -> memory amplification DoS (httputil.py:34) · Advisory · tornadoweb/tornado · GitHub

https://github.com/tornadoweb/tornado/security/advisories/GHSA-8423-8fgw-73vq

Vendor Advisories for CVE-2026-91990(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 (83 versions)6.5.8—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 18× in last 7d / 18× 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. 2026-09-19 01:23 UTCEG score recompute
  2. 2026-09-19 01:23 UTCGHSA enrichment
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 13:28 UTCGHSA enrichment
  5. 2026-09-18 01:32 UTCEG score recompute
  6. 2026-09-18 01:32 UTCGHSA enrichment
  7. 2026-09-17 19:32 UTCEPSS rescore
  8. 2026-09-17 13:36 UTCGHSA enrichment
  9. 2026-09-17 01:40 UTCEG score recompute
  10. 2026-09-17 01:40 UTCGHSA enrichment
  11. 2026-09-16 14:09 UTCEPSS rescore
  12. 2026-09-16 13:44 UTCGHSA enrichment
  13. 2026-09-16 05:28 UTCEG score recompute
  14. 2026-09-16 05:28 UTCGHSA enrichment
  15. 2026-09-15 17:32 UTCEG score recompute
  16. 2026-09-15 16:18 UTCEG score recompute
  17. 2026-09-15 15:23 UTCEG score recompute
  18. 2026-09-15 15:22 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-91990?
CVE-2026-91990 is a high vulnerability published on September 15, 2026. Tornado before 6.5.8 contains a memory amplification vulnerability in parsemultipartformdata that splits multipart data before validating the maxparts limit. Attackers can send crafted multipart requests with many parts to create large transient lists, exhausting server memory and causing denial of…
When was CVE-2026-91990 disclosed?
CVE-2026-91990 was first published in the National Vulnerability Database on September 15, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-91990 actively exploited?
CVE-2026-91990 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 64.8% of all scored CVEs.
What is the CVSS score of CVE-2026-91990?
CVE-2026-91990 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-91990?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-91990, 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-2026-91990

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