CVE-2026-15076: In versions up to and including 4.5.29 (4.x branch) and 5.1.4 (5.x branch), the WebClientSession component of

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-15076 is a high-severity flaw (CVSS 7.5) affecting vert.x. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In versions up to and including 4.5.29 (4.x branch) and 5.1.4 (5.x branch), the WebClientSession component of Eclipse Vert.x Web Client does not validate that the Domain attribute of a Set-Cookie response header matches the originating server's domain, in violation of RFC 6265 section 5.3. An attacker who controls any server that the victim application contacts can inject a cookie scoped to an arbitrary third-party domain; because the session sto

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 91%)
CISA exploited list	No
Weakness	CWE-346
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 vert.x UPGRADE

Affected: >= 4.0.0 and <= 4.5.29 · >= 5.0.0 and <= 5.1.4

Fixed in: newer than 5.1.4

Safe to downgrade to: a release before 4.0.0

1. Check installed version

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

2. UPGRADE to newer than 5.1.4 (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 4.0.0 (Debian / Ubuntu)

apt-cache madison vert.x sudo apt install vert.x=<VERSION_BEFORE_4.0.0> 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_4.0.0> 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-2026-15076?

vert.x: upgrade to newer than 5.1.4. Exact commands for each OS are on this page.

Is CVE-2026-15076 being exploited?

CVE-2026-15076 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-2026-15076 affect?

CVE-2026-15076 affects vert.x. Severity is high (CVSS 7.5). In versions up to and including 4.5.29 (4.x branch) and 5.1.4 (5.x branch), the WebClientSession component of Eclipse Vert.x Web Client does not validate that the Domain attribute of a Set-Cookie response header matches the originating serv

How urgent is CVE-2026-15076?

Priority 33/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-15075 HIGH 7.5 UPGRADE In Eclipse Vert.x versions up to and including 4.5.29 (4.x branch) and 5.1.4 (5.x branch), DefaultRedirectHand

References

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