CVE-2026-100661

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 4.2.0.Final through 4.2.17.Final contain a denial-of-service vulnerability in the QPACK prefixed-integer decoder (QpackUtil.decodePrefixedInteger), which does not bound the number of continuation bytes it will process. A remote, unauthenticated peer can open a QPACK unidirectional stream (type 0x02 encoder or 0x03 decoder) and send a first byte with all prefix bits set (e.g. 0xFF for a 7-bit prefix or 0x3F for a 5-bit prefix) followed by an endless run of 0x80 continuation bytes. The decoder returns -1 ('need more bytes'), so callers never consume the input, the ByteToMessageDecoder cumulator grows without bound, and each decode() invocation re-scans the whole accumulated buffer, yielding O(N^2) CPU cost. The result is unbounded per-connection heap growth (OutOfMemoryError) and event-loop CPU starvation, reachable in every configuration. 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
25th
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

October 2, 2026

Advisory Details (2)

Auto-updated Sep 26, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation | Advisories | VulnCheck

https://www.vulncheck.com/advisories/netty-http-3-qpack-prefixed-integer-dos-via-unbounded-accumulation
github Patch Available🟡 PoC Available

Netty HTTP/3 QPACK non-terminating prefixed integer causes unbounded accumulation and O(n^2) DoS · Advisory · netty/netty · GitHub

https://github.com/netty/netty/security/advisories/GHSA-v5p2-hmgx-3xrx

Vendor Advisories for CVE-2026-100661(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 31× in last 7d / 43× 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. 2026-10-05 07:52 UTCEG score recompute
  2. 2026-10-05 07:52 UTCGHSA enrichment
  3. 2026-10-04 23:21 UTCEPSS rescore
  4. 2026-10-04 20:12 UTCGHSA enrichment
  5. 2026-10-04 08:29 UTCGHSA enrichment
  6. 2026-10-03 20:48 UTCEG score recompute
  7. 2026-10-03 20:48 UTCGHSA enrichment
  8. 2026-10-03 14:25 UTCEPSS rescore
  9. 2026-10-03 09:08 UTCGHSA enrichment
  10. 2026-10-02 21:24 UTCEG score recompute
  11. 2026-10-02 21:24 UTCGHSA enrichment
  12. 2026-10-02 20:55 UTCEG score recompute
  13. 2026-10-02 20:55 UTCGHSA enrichment
  14. 2026-10-02 12:50 UTCGHSA enrichment
  15. 2026-10-02 01:10 UTCEG score recompute
  16. 2026-10-02 01:10 UTCGHSA enrichment
  17. 2026-10-01 19:49 UTCEPSS rescore
  18. 2026-10-01 13:30 UTCGHSA enrichment
  19. 2026-10-01 01:50 UTCEG score recompute
  20. 2026-10-01 01:50 UTCGHSA enrichment
  21. 2026-09-30 15:02 UTCEPSS rescore
  22. 2026-09-30 14:10 UTCGHSA enrichment
  23. 2026-09-30 02:29 UTCEG score recompute
  24. 2026-09-30 02:29 UTCGHSA enrichment
  25. 2026-09-29 15:20 UTCEPSS rescore
Show 18 more
  1. 2026-09-29 14:49 UTCGHSA enrichment
  2. 2026-09-29 03:08 UTCEG score recompute
  3. 2026-09-29 03:08 UTCGHSA enrichment
  4. 2026-09-28 15:27 UTCEG score recompute
  5. 2026-09-28 15:27 UTCGHSA enrichment
  6. 2026-09-28 13:50 UTCEPSS rescore
  7. 2026-09-28 05:04 UTCGHSA enrichment
  8. 2026-09-27 17:24 UTCEG score recompute
  9. 2026-09-27 17:24 UTCGHSA enrichment
  10. 2026-09-27 16:36 UTCEG score recompute
  11. 2026-09-27 16:35 UTCGHSA enrichment
  12. 2026-09-27 13:57 UTCEG score recompute
  13. 2026-09-27 13:56 UTCGHSA enrichment
  14. 2026-09-27 02:13 UTCEG score recompute
  15. 2026-09-27 02:13 UTCGHSA enrichment
  16. 2026-09-26 14:33 UTCEG score recompute
  17. 2026-09-26 13:37 UTCEG score recompute
  18. 2026-09-26 13:30 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-100661?
CVE-2026-100661 is a high vulnerability published on September 26, 2026. Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final contain a denial-of-service vulnerability in the QPACK prefixed-integer decoder (QpackUtil.decodePrefixedInteger), which does not bound the number of continuation bytes it will process. A remote,…
When was CVE-2026-100661 disclosed?
CVE-2026-100661 was first published on September 26, 2026, with the most recent update on October 2, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100661 actively exploited?
CVE-2026-100661 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (25th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100661?
CVE-2026-100661 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-2026-100661?
A fix for CVE-2026-100661 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-100661 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-100661

Explore →

Is Your Infrastructure Affected by CVE-2026-100661?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Book a Demo →Browse All CVEs