8.7

CVE-2026-75596: netty Inefficient Algorithmic Complexity

CVSS: 8.7v4.0HighAnalyzed
AliasesUBUNTU-CVE-2026-75596DEBIAN-CVE-2026-75596CGA-22m9-pq9j-g5c8
Published 19-08-2026Last modified 20-08-2026
Open JSON

Vulnerability summary

CVE-2026-75596 is a high (CVSS 8.7) Inefficient Algorithmic Complexity vulnerability in netty. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.8% of scored vulnerabilities.

Overall risk
35/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.7/10
010
High · v4.0 (CVE.org)
EPSS score
0.37%
0%100%
Low · +0.02 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 2
OPENSUSE-SU-2026:11882-1SUSE-SU-2026:4391-1

Timeline

  1. 19-08-2026
    PublishedVulnerability first disclosed.
  2. 20-08-2026
    Last modifiedVulnerability information updated.

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Final and 4.2.17.Final, the default io.netty.handler.ssl.SniHandler constructors use the pre-handshake ClientHello aggregation path in handler/src/main/java/io/netty/handler/ssl/SslClientHelloHandler.java at io.netty.handler.ssl.SslClientHelloHandler#decode, where handshakeBuffer.clear() and writeBytes() recopy all previously received body bytes for every additional TLS record. An unauthenticated remote peer can advertise a large ClientHello and deliver its body in thousands of tiny records, causing quadratic CPU work on the event loop before the TLS handshake completes and degrading TLS handling for other clients. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

CVSS metrics

9 scores · 7 sources · 2 versions

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

30%

Versus all other CVEs

30-day change

+0.02 pp

From 0.35% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.37%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard141 products
  • akhq< 0.28.0-r8
  • apache-camel-karavan-devmode< 4.18.1-r12
  • apache-hop< 2.19.0-r3
  • apache-nifi-2.11< 2.11.0-r7
  • cassandra-5.0< 5.0.9-r7
Wolfi32 products
  • akhq< 0.28.0-r8
  • cassandra-5.0< 5.0.9-r7
  • cassandra-reaper< 5.0.1-r1
  • celeborn-0.6All versions (No fix recorded)
  • druid< 37.0.0-r56
Debian1 product
  • nettyAll versions (No fix recorded)
Io.netty1 product
  • netty-handler≥ 4.2.0.Final, < 4.2.17.Final | < 4.1.137.Final
Netty1 product
  • netty< 4.1.137.Final | ≥ 4.2.0.Final, < 4.2.17.Final | < 4.1.137 | ≥ 4.2.0, < 4.2.17
Ubuntu1 product
  • nettyAll versions (No fix recorded)

6 vendors · 177 products

References

13 links
Show all 13 references