CVE-2026-12606: Eclipse Grizzly in versions before 5.0.2, cannot properly parse the trailer section in malformed trailer heade

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-12606 is a medium-severity flaw (CVSS 5.3) affecting grizzly. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Eclipse Grizzly in versions before 5.0.2, cannot properly parse the trailer section in malformed trailer header's line, which can be leveraged to perform HTTP request smuggling. Grizzly 5.0.1 supports system properties that enable the behavior that fixes the vulnerability - set org.glassfish.grizzly.http.STRICT_HEADER_NAME_VALIDATION_RFC_9110 and org.glassfish.grizzly.http.STRICT_HEADER_VALUE_VALIDATION_RFC_9110 system properties to "true".

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 79%)
CISA exploited list	No
Weakness	CWE-444
Published	2026-07-14
Last modified	2026-10-24

Publisher (CNA): Eclipse Foundation · Vendor: eclipse

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-14 09:16 UTCPublished CVE record published
2026-10-24 22:10 UTCUpdated Record last modified

eclipse grizzly UPGRADE

Affected: >= 4.0.0 and <= 4.0.2 · >= 5.0.0 and < 5.0.2

Fixed in: 5.0.2

Safe to downgrade to: a release before 4.0.0

1. Check installed version

apt-cache policy grizzly || rpm -q grizzly || grizzly --version

2. UPGRADE to 5.0.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade grizzly

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade grizzly

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 4.0.0 (Debian / Ubuntu)

apt-cache madison grizzly sudo apt install grizzly=<VERSION_BEFORE_4.0.0> sudo apt-mark hold grizzly

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list grizzly sudo dnf downgrade grizzly-<VERSION_BEFORE_4.0.0> sudo dnf versionlock add grizzly

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-2026-12606?

grizzly: upgrade to 5.0.2. Exact commands for each OS are on this page.

Is CVE-2026-12606 being exploited?

CVE-2026-12606 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-2026-12606 affect?

CVE-2026-12606 affects grizzly. Severity is medium (CVSS 5.3). Eclipse Grizzly in versions before 5.0.2, cannot properly parse the trailer section in malformed trailer header's line, which can be leveraged to perform HTTP request smuggling. Grizzly 5.0.1 supports system properties that enable the behav

How urgent is CVE-2026-12606?

Priority 29/100. Remotely exploitable, no login, no user action

References

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