CVE-2021-34801: Valine 1.4.14 allows remote attackers to cause a denial of service (application outage) by supplying a ua (aka

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MEDIUM 5.3REMOTEDOWNGRADE

CVE-2021-34801 is a medium-severity flaw (CVSS 5.3) affecting valine. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Valine 1.4.14 allows remote attackers to cause a denial of service (application outage) by supplying a ua (aka User-Agent) value that only specifies the product and version.

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.7% (top 23%)
CISA exploited list	No
Published	2021-06-16
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: valine.js

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

Am I affected?

Timeline

2021-06-16 15:15 UTCPublished CVE record published
2026-06-17 03:56 UTCUpdated Record last modified

valine.js valine DOWNGRADE

Affected: 1.4.14

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.4.14

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.4.14 (Debian / Ubuntu)

apt-cache madison valine sudo apt install valine=<VERSION_BEFORE_1.4.14> sudo apt-mark hold valine

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list valine sudo dnf downgrade valine-<VERSION_BEFORE_1.4.14> sudo dnf versionlock add valine

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-2021-34801?

valine: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-34801 being exploited?

CVE-2021-34801 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-2021-34801 affect?

CVE-2021-34801 affects valine. Severity is medium (CVSS 5.3). Valine 1.4.14 allows remote attackers to cause a denial of service (application outage) by supplying a ua (aka User-Agent) value that only specifies the product and version.

How urgent is CVE-2021-34801?

Priority 48/100. Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2022-38545 CRITICAL 9.6 DOWNGRADE Valine v1.4.18 was discovered to contain a remote code execution (RCE) vulnerability which allows attackers to
CVE-2020-28847 MEDIUM 5.4 DOWNGRADE Cross Site Scripting (XSS) vulnerability in xCss Valine v1.4.14 via the nick parameter to /classes/Comment.

References

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