CVE-2026-100664

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-26. A secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.2.Final through 4.2.17.Final builds the HTTP/3 :authority pseudo-header from the HTTP/1 Host header before considering the authority of an absolute-form HTTP/1 request-target. In HttpConversionUtil.toHttp3Headers(HttpMessage, boolean) — reached via Http3FrameToHttpObjectCodec(false) — a non-empty Host header takes precedence over the request-target authority, contrary to the HTTP/1.1 rule that a server receiving an absolute-form request-target must ignore the Host header. In a Netty-based HTTP/1-to-HTTP/3 gateway, proxy, or protocol bridge, a remote client can send a request such as "GET https://trusted.example/admin HTTP/1.1" with "Host: attacker.example", causing components that validate, authorize, or route on the RFC-defined request-target authority to reach a different decision than the upstream HTTP/3 peer, which receives :authority derived from the conflicting Host header. This authority confusion can affect virtual-host routing, allow-list checks, backend selection, cache keys, and URL generation. The advisory reports integrity impact only (no code execution, memory corruption, or availability impact). Fixed in 4.2.18.Final.

CVSS v3
7.5
EG Score
7.5HIGHhigh confidence
EG Risk
49
EG Risk 49/100CISA SSVC

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%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
23rd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 26, 2026

Last Modified

September 28, 2026

Advisory Details (2)

Auto-updated Sep 26, 2026
Patch available. Sources: github.
generic

Netty 4.2.2 through 4.2.15 HTTP/1 Host Header Authority Confusion | Advisories | VulnCheck

https://www.vulncheck.com/advisories/netty-4.2.2-through-4.2.15-http-1-host-header-authority-confusion
github Patch Available

HTTP/1 absolute-form Host mismatch is translated to HTTP/3 :authority, overriding the request-target authority · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-hfr2-x62w-v49h

Vendor Advisories for CVE-2026-100664(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 34× in last 7d / 40× 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. 2026-10-04 08:27 UTCGHSA enrichment
  2. 2026-10-03 21:14 UTCEG score recompute
  3. 2026-10-03 21:14 UTCGHSA enrichment
  4. 2026-10-03 14:25 UTCEPSS rescore
  5. 2026-10-03 10:01 UTCGHSA enrichment
  6. 2026-10-02 22:47 UTCEG score recompute
  7. 2026-10-02 22:47 UTCGHSA enrichment
  8. 2026-10-02 11:32 UTCGHSA enrichment
  9. 2026-10-02 00:14 UTCEG score recompute
  10. 2026-10-02 00:14 UTCGHSA enrichment
  11. 2026-10-01 19:49 UTCEPSS rescore
  12. 2026-10-01 13:01 UTCGHSA enrichment
  13. 2026-10-01 01:48 UTCEG score recompute
  14. 2026-10-01 01:48 UTCGHSA enrichment
  15. 2026-09-30 15:02 UTCEPSS rescore
  16. 2026-09-30 14:36 UTCGHSA enrichment
  17. 2026-09-30 03:18 UTCGHSA enrichment
  18. 2026-09-29 16:06 UTCEG score recompute
  19. 2026-09-29 16:06 UTCGHSA enrichment
  20. 2026-09-29 15:20 UTCEPSS rescore
  21. 2026-09-29 04:52 UTCEG score recompute
  22. 2026-09-29 04:52 UTCGHSA enrichment
  23. 2026-09-28 17:40 UTCEG score recompute
  24. 2026-09-28 17:39 UTCGHSA enrichment
  25. 2026-09-28 17:00 UTCEG score recompute
Show 15 more
  1. 2026-09-28 17:00 UTCGHSA enrichment
  2. 2026-09-28 15:27 UTCEG score recompute
  3. 2026-09-28 15:27 UTCGHSA enrichment
  4. 2026-09-28 13:50 UTCEPSS rescore
  5. 2026-09-28 04:38 UTCGHSA enrichment
  6. 2026-09-27 17:24 UTCEG score recompute
  7. 2026-09-27 17:24 UTCGHSA enrichment
  8. 2026-09-27 16:35 UTCEG score recompute
  9. 2026-09-27 16:35 UTCGHSA enrichment
  10. 2026-09-27 13:01 UTCGHSA enrichment
  11. 2026-09-27 01:48 UTCEG score recompute
  12. 2026-09-27 01:47 UTCGHSA enrichment
  13. 2026-09-26 14:33 UTCEG score recompute
  14. 2026-09-26 13:37 UTCEG score recompute
  15. 2026-09-26 13:30 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-100664?
CVE-2026-100664 is a high vulnerability published on September 26, 2026. Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.2.Final through 4.2.17.Final builds the HTTP/3 :authority pseudo-header from the HTTP/1 Host header before considering the authority of an absolute-form HTTP/1 request-target. In HttpConversionUtil.toHttp3Headers(HttpMessage, boolean) —…
When was CVE-2026-100664 disclosed?
CVE-2026-100664 was first published on September 26, 2026, with the most recent update on September 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100664 actively exploited?
CVE-2026-100664 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (23rd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100664?
CVE-2026-100664 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-100664?
A fix for CVE-2026-100664 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-100664 are linked in the Vendor Advisories panel on this page.

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