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CVE-2026-59903 Netty

Affected softwareNetty
Severity7.5 High CVSS 3.1 2 scores
Fixed in4.2.17.Final, 4.1.137.Final
WeaknessCWE-524
Published17 Aug 2026
Updated23 Sep 2026

Published 2 months ago. NVD often adds the list of affected products days or weeks after a CVE is published, and the other sources we check lag too. The scope and status here may change.

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, io.netty.handler.codec.http.cors.CorsHandler setVaryHeader replaces application Vary headers such as Authorization or Cookie with Origin, allowing a caching proxy or CDN to reuse authenticated responses across users and disclose sensitive information. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

Exploitation status

No public exploit

No exploit has been reported in the sources we check. The 1 repository below are public GitHub repositories with fewer than 5 stars.

  • CISA KEV not listed
  • VulnCheck KEV not listed
  • CISA Vulnrichment exploitation: none
  • Indexed PoC 1 indexed, none at 5+ stars
  • EPSS 0.32% chance in 30 days

1 of these are GitHub repositories with fewer than 5 stars. They are listed for reference and don't count toward the exploitation status above.

IndexArtifactStarsFirst seen
GitHub PoC CVE-2026-59903 / CVE-2026-33870: offline checker for io.netty:netty-codec-http - its 14 CVEs plus 9 advisories Netty published on 2026-09-10 that the GitHub Advisory Database (Dependabot) does not list. 4.1.137.Final / 4.2.17.Final is no longer enough; upgrade to 4.1.138.Final / 4.2.18.Final. 2026-09-08

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

A public code fix exists: netty/netty #17213.

  • Protection none
  • Action unverified
  • Review automated Upstream data
  • Record active
Decided by Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all
Finding This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.
Candidate fix https://github.com/netty/netty/pull/17213 : a pull request: the change under review

CVSS

7.5 HIGH v3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N 2 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

VersionScoreBandVectorAssignerType
CVSS 3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N NVD Primary published
CVSS 3.1 6.5 MEDIUM CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N security-advisories@github.com Secondary

Affected software and releases

Oracle advisories

AdvisoryTypeQuarterProducts Oracle names in its risk matrix
Oracle Critical Patch Update October 2026 ↗ CPU 2026-Q4 Oracle Communications / Core (Netty) (6.1.1-7.0.0)

Oracle components and versions

FamilyComponentVersions, as Oracle lists themRead as
Oracle Communications Core (Netty) 6.1.1-7.0.0

Maven packages

Affected and fixed versions, from OSV.dev
PackageIntroducedFixedLast affected
io.netty:netty-codec-http 4.2.0.Final 4.2.17.Final unbounded
io.netty:netty-codec-http 0 4.1.137.Final unbounded

Products and versions

2 products, 4 version entries
SourceVendorProductSchemeAffected versions
osv io.netty netty-codec-http generic < 4.1.137 · ≥ 4.2.0 and < 4.2.17
nvd netty netty generic < 4.1.137 · ≥ 4.2.0 and < 4.2.17

References

URLTags
https://github.com/netty/netty/pull/17213 pr
https://github.com/netty/netty/security/advisories/GHSA-8c42-7qj2-3j46 WEB
https://github.com/netty/netty/pull/17217 WEB
https://github.com/netty/netty PACKAGE
https://github.com/netty/netty/releases/tag/netty-4.1.137.Final WEB
https://github.com/netty/netty/releases/tag/netty-4.2.17.Final WEB

Timeline

Published2026-08-17By the CVE Program.
NVD record modified2026-09-23NVD's own last-modified date for this record.