CVE-2021-34817: A Cross-Site Scripting (XSS) issue in the chat component of Etherpad 1.8.13 allows remote attackers to inject

This month

MEDIUM 6.1DOWNGRADE

CVE-2021-34817 is a medium-severity flaw (CVSS 6.1) affecting etherpad. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A Cross-Site Scripting (XSS) issue in the chat component of Etherpad 1.8.13 allows remote attackers to inject arbitrary JavaScript or HTML by importing a crafted pad.

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	1.3% (top 29%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-07-19
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: etherpad

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

Am I affected?

Timeline

2021-07-19 14:15 UTCPublished CVE record published
2026-06-17 03:56 UTCUpdated Record last modified

etherpad etherpad DOWNGRADE

Affected: 1.8.13

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.8.13

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.8.13 (Debian / Ubuntu)

apt-cache madison etherpad sudo apt install etherpad=<VERSION_BEFORE_1.8.13> sudo apt-mark hold etherpad

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

dnf --showduplicates list etherpad sudo dnf downgrade etherpad-<VERSION_BEFORE_1.8.13> sudo dnf versionlock add etherpad

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-2021-34817?

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

Is CVE-2021-34817 being exploited?

CVE-2021-34817 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-2021-34817 affect?

CVE-2021-34817 affects etherpad. Severity is medium (CVSS 6.1). A Cross-Site Scripting (XSS) issue in the chat component of Etherpad 1.8.13 allows remote attackers to inject arbitrary JavaScript or HTML by importing a crafted pad.

How urgent is CVE-2021-34817?

Priority 44/100. Public exploit reference

Related CVEs

CVE-2021-43802 CRITICAL 9.9 UPGRADE Etherpad is a real-time collaborative editor
CVE-2021-34816 HIGH 7.2 DOWNGRADE An Argument Injection issue in the plugin management of Etherpad 1.8.13 allows privileged users to execute arb
CVE-2020-22785 HIGH 7.5 UPGRADE Etherpad < 1.8.3 is affected by a missing lock check which could cause a denial of service
CVE-2020-22783 MEDIUM 6.5 UPGRADE Etherpad <1.8.3 stored passwords used by users insecurely in the database and in log files
CVE-2020-22782 HIGH 7.5 UPGRADE Etherpad < 1.8.3 is affected by a denial of service in the import functionality

References

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