CVE-2020-21496: A cross-site scripting (XSS) vulnerability in the component /admin/?setting-base.htm of Xiuno BBS 4.0.4 allows

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MEDIUM 6.1DOWNGRADE

CVE-2020-21496 is a medium-severity flaw (CVSS 6.1) affecting xiunobbs. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A cross-site scripting (XSS) vulnerability in the component /admin/?setting-base.htm of Xiuno BBS 4.0.4 allows attackers to execute arbitrary web scripts or HTML via the sitebrief parameter.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-10-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: xiuno

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

Am I affected?

Timeline

2021-10-04 21:15 UTCPublished CVE record published
2026-06-17 03:03 UTCUpdated Record last modified

xiuno xiunobbs DOWNGRADE

Affected: 4.0.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0.4

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.0.4 (Debian / Ubuntu)

apt-cache madison xiunobbs sudo apt install xiunobbs=<VERSION_BEFORE_4.0.4> sudo apt-mark hold xiunobbs

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

dnf --showduplicates list xiunobbs sudo dnf downgrade xiunobbs-<VERSION_BEFORE_4.0.4> sudo dnf versionlock add xiunobbs

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-2020-21496?

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

Is CVE-2020-21496 being exploited?

CVE-2020-21496 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-2020-21496 affect?

CVE-2020-21496 affects xiunobbs. Severity is medium (CVSS 6.1). A cross-site scripting (XSS) vulnerability in the component /admin/?setting-base.htm of Xiuno BBS 4.0.4 allows attackers to execute arbitrary web scripts or HTML via the sitebrief parameter.

How urgent is CVE-2020-21496?

Priority 40/100. Public exploit reference

Related CVEs

CVE-2020-21495 MEDIUM 6.1 DOWNGRADE A cross-site scripting (XSS) vulnerability in the component /admin/?setting-base.htm of Xiuno BBS 4.0.4 allows
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CVE-2020-21493 MEDIUM 5.3 DOWNGRADE An issue in the component route\user.php of Xiuno BBS v4.0.4 allows attackers to enumerate usernames.
CVE-2020-19914 MEDIUM 6.1 DOWNGRADE Cross Site Scripting (XSS) in xiunobbs 4.0.4 allows remote attackers to execute arbitrary web script or HTML v

References

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