CVE-2026-102479: In Eclipse Vert.x versions [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the Vert.x HTTP/1.x decoder uses

Routine

MEDIUM 5.9REMOTEUPGRADE

CVE-2026-102479 is a medium-severity flaw (CVSS 5.9) affecting vert.x. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Eclipse Vert.x versions [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the Vert.x HTTP/1.x decoder uses a canonicalization for well known HTTP headers, the canonicalization process interprets well crafted headers as headers of this list, allowing for instance Content-Xength to be interpeted as Content-Length. This can be exploited for request smuggling purpose. The impacted component is io.vertx:vertx-core.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 81%)
CISA exploited list	No
Weakness	CWE-444
Published	2026-10-14
Last modified	2026-10-20

Publisher (CNA): Eclipse Foundation · Vendor: eclipse

Last updated 2026-10-20 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-14 19:17 UTCPublished CVE record published
2026-10-20 19:31 UTCUpdated Record last modified

eclipse vert.x UPGRADE

Affected: >= 5.0.0 and < 5.1.10 · 5.2.0

Fixed in: 5.1.10

Safe to downgrade to: a release before 5.0.0

1. Check installed version

apt-cache policy vert.x || rpm -q vert.x || vert.x --version

2. UPGRADE to 5.1.10 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade vert.x

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade vert.x

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 5.0.0 (Debian / Ubuntu)

apt-cache madison vert.x sudo apt install vert.x=<VERSION_BEFORE_5.0.0> sudo apt-mark hold vert.x

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

dnf --showduplicates list vert.x sudo dnf downgrade vert.x-<VERSION_BEFORE_5.0.0> sudo dnf versionlock add vert.x

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-2026-102479?

vert.x: upgrade to 5.1.10. Exact commands for each OS are on this page.

Is CVE-2026-102479 being exploited?

CVE-2026-102479 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-2026-102479 affect?

CVE-2026-102479 affects vert.x. Severity is medium (CVSS 5.9). In Eclipse Vert.x versions [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the Vert.x HTTP/1.x decoder uses a canonicalization for well known HTTP headers, the canonicalization process interprets well crafted headers as headers of this l

How urgent is CVE-2026-102479?

Priority 30/100. Remotely exploitable, no login, no user action

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References

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