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CVE-2026-48059: Netty is a network application framework for development of protocol servers and clients

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HIGH 7.5REMOTEUPGRADE

CVE-2026-48059 is a high-severity flaw (CVSS 7.5) affecting netty. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, the HAProxy PROXY protocol v2 codec in netty leaks native or heap memory on every connection when a client sends a syntactically valid header containing nested `PP2_TYPE_SSL` TLVs (type-length-value records) at depth two or greater. The leak occurs on the successful parse path — no exception is thrown, the me

Why this priority

  • High severity
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score7.5 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance0.6% (top 50%)
CISA exploited listNo
WeaknessCWE-401, CWE-1286
Published2026-06-12
Last modified2026-09-18
Publisher (CNA): GitHub, Inc. · Vendor: netty

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Last updated 2026-09-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

netty netty UPGRADE
Affected: < 4.1.135 · >= 4.2.0 and < 4.2.15
Fixed in: 4.1.135, 4.2.15
Safe to downgrade to: a release before 4.2.0
1. Check installed version
apt-cache policy netty || rpm -q netty || netty --version
2. UPGRADE to 4.1.135 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade netty
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade netty
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 4.2.0 (Debian / Ubuntu)
apt-cache madison netty sudo apt install netty=<VERSION_BEFORE_4.2.0> sudo apt-mark hold netty
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list netty sudo dnf downgrade netty-<VERSION_BEFORE_4.2.0> sudo dnf versionlock add netty
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-48059?

netty: upgrade to 4.1.135, 4.2.15. Exact commands for each OS are on this page.

Is CVE-2026-48059 being exploited?

CVE-2026-48059 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-48059 affect?

CVE-2026-48059 affects netty. Severity is high (CVSS 7.5). Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, the HAProxy PROXY protocol v2 codec in netty leaks native or heap memory on every connection when a

How urgent is CVE-2026-48059?

Priority 44/100. High severity; Remotely exploitable, no login, no user action

Software pages

HAProxy vulnerabilities

Related CVEs

References

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