Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-89044

CVE-2026-89044MEDIUM

Netty 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final HTTP Request Smuggling via Transfer-Encoding

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   N   N   N   L   L   N    6.9   .0028   19.0     —

AFFECTED
  Product  Versions         Fixed
  netty    4.1.133.Final –  —

TIMELINE
  Sep 10  Reserved by VulnCheck
  Sep 10  Published (CNA: VulnCheck)
  Sep 16  EXPLOIT PUBLISHED — CVE-2026-89044 (netty). Public exploit reference added.
  Sep 18  EXPLOIT PUBLISHED — CVE-2026-89044 (netty). Public exploit reference added.

CWE-444 · CNA: VulnCheck · CVSS v4.0 · 8 references · NVD status: Analyzed

Description

Netty versions 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final fail to properly validate the final transfer coding in the Transfer-Encoding header, allowing attackers to smuggle requests by using malformed encoding declarations. Attackers can split Transfer-Encoding headers across multiple lines or use values like 'chunked, xchunked' to bypass validation and decode messages as chunked when the final coding is not chunked, enabling request smuggling attacks.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
September 10, 2026	Reserved	Reserved by VulnCheck
September 10, 2026	Published	Published (CNA: VulnCheck)
September 16, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-89044 (netty). Public exploit reference added.
September 18, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-89044 (netty). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
netty	netty	—	4.1.133.Final	—

Weaknesses

CWE-444

References (8)

https://github.com/netty/netty [Product]
https://github.com/netty/netty/blob/netty-4.1.137.Final/codec-http/src/main/java/io/netty/handler/codec/http/HttpObjectDecoder.java#L866 [Product]
https://github.com/netty/netty/commit/640d4d3324f7b811a4903d0730c8ccb35500500c [Patch]
https://github.com/netty/netty/commit/ca87393b0e9e13c493d213a268e727a6d44e1585 [Patch]
https://github.com/netty/netty/releases/tag/netty-4.1.138.Final [Release Notes]
https://github.com/netty/netty/releases/tag/netty-4.2.18.Final [Release Notes]
https://github.com/netty/netty/security/advisories/GHSA-hcvj-94mj-jp5c [Exploit, Vendor Advisory]
https://www.vulncheck.com/advisories/netty-4.1.133-final-through-4.1.137-final-and-4.2.13-final-through-4.2.17-final-http-request-smuggling-via-transfer-encoding [Patch, Third Party Advisory]

Authoritative record: CVE-2026-89044 at cve.org

Vendors: netty

Weaknesses: CWE-444

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-89044 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.