CVE-2025-6703: Improper Input Validation vulnerability in Mozilla neqo leads to an unexploitable crash..This issue affects ne

Routine

MEDIUM 6.5UPGRADE

CVE-2025-6703 is a medium-severity flaw (CVSS 6.5) affecting neqo. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Input Validation vulnerability in Mozilla neqo leads to an unexploitable crash..This issue affects neqo: from 0.4.24 through 0.13.2.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 84%)
CISA exploited list	No
Weakness	CWE-20
Published	2025-06-26
Last modified	2026-06-17

Publisher (CNA): Mozilla Corporation · Vendor: mozilla

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-06-26 10:15 UTCPublished CVE record published
2026-06-17 10:02 UTCUpdated Record last modified

mozilla neqo UPGRADE

Affected: >= 0.4.24 and <= 0.13.2

Fixed in: newer than 0.13.2

Safe to downgrade to: a release before 0.4.24

1. Check installed version

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

2. UPGRADE to newer than 0.13.2 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade neqo

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 0.4.24 (Debian / Ubuntu)

apt-cache madison neqo sudo apt install neqo=<VERSION_BEFORE_0.4.24> sudo apt-mark hold neqo

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

dnf --showduplicates list neqo sudo dnf downgrade neqo-<VERSION_BEFORE_0.4.24> sudo dnf versionlock add neqo

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-2025-6703?

neqo: upgrade to newer than 0.13.2. Exact commands for each OS are on this page.

Is CVE-2025-6703 being exploited?

CVE-2025-6703 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-2025-6703 affect?

CVE-2025-6703 affects neqo. Severity is medium (CVSS 6.5). Improper Input Validation vulnerability in Mozilla neqo leads to an unexploitable crash..This issue affects neqo: from 0.4.24 through 0.13.2.

How urgent is CVE-2025-6703?

Priority 27/100. No elevated risk signals yet.

References

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