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CVE-2026-55831

Netty SPDY SETTINGS frame count materializes unbounded settings map

HIGH
7.5
CVSS Score
Published: July 20, 2026 at 11:00 PM UTC
Updated: July 23, 2026 at 09:12 PM UTC
1 product affected across 1 vendorNetty

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Severity
HIGH7.5
Exploit prediction
EPSS 0.7%
SSVC
PoC

Description

Netty is a network application framework for development of protocol servers and clients. Prior to 4.1.136.Final and 4.2.16.Final, Netty's SPDY SETTINGS decoder accepts a peer-declared SETTINGS entry count up to the 24-bit frame-length limit and materializes every unique setting ID in `DefaultSpdySettingsFrame`, allowing a remote SPDY/3.1 peer to send a syntactically valid roughly 2 MiB SETTINGS frame that creates 262144 map entries and amplifies network input into heap growth and ordered-map insertion work. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Netty· Nettymaven
95%
v < 4.1.136.Finalv < 4.2.16.Final4.1.0 ≤ v < 4.1.1364.2.0 ≤ v < 4.2.16
Affected range stops below 4.1.136, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.1.136.Final, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.2.16, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.2.16.Final, so it looks safe — our inference, not a vendor statement

References (5)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/netty/netty/security/advisories/GHSA-6jqx-86gh-f27w
x_refsource_MISCPatch
Source: cverecord
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b
x_refsource_MISCPatch
Source: cverecord
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-770CWE-400

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