CVE-2021-43802: Etherpad is a real-time collaborative editor

Q: How do I fix CVE-2021-43802?

etherpad: upgrade to 1.8.16. Exact commands for each OS are on this page.

Q: Is CVE-2021-43802 being exploited?

CVE-2021-43802 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-43802 affect?

CVE-2021-43802 affects etherpad. Severity is critical (CVSS 9.9). Etherpad is a real-time collaborative editor. In versions prior to 1.8.16, an attacker can craft an `*.etherpad` file that, when imported, might allow the attacker to gain admin privileges for the Etherpad instance. This, in turn, can be us

Q: How urgent is CVE-2021-43802?

Priority 55/100. Critical severity

This month

CRITICAL 9.9UPGRADE

CVE-2021-43802 is a critical-severity flaw (CVSS 9.9) affecting etherpad. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Etherpad is a real-time collaborative editor. In versions prior to 1.8.16, an attacker can craft an `*.etherpad` file that, when imported, might allow the attacker to gain admin privileges for the Etherpad instance. This, in turn, can be used to install a malicious Etherpad plugin that can execute arbitrary code (including system commands). To gain privileges, the attacker must be able to trigger deletion of `express-session` state or wait for ol

Why this priority

Critical severity

A fixed release or distro patch exists.

Risk facts

CVSS score	9.9 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	2.1% (top 19%)
CISA exploited list	No
Weakness	CWE-790, CWE-1287, CWE-20
Published	2021-12-09
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: etherpad

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

Am I affected?

Timeline

2021-12-09 23:15 UTCPublished CVE record published
2026-06-17 04:11 UTCUpdated Record last modified

etherpad etherpad UPGRADE

Affected: < 1.8.16

Fixed in: 1.8.16

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.8.16 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade etherpad

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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-2021-43802?

etherpad: upgrade to 1.8.16. Exact commands for each OS are on this page.

Is CVE-2021-43802 being exploited?

CVE-2021-43802 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-2021-43802 affect?

CVE-2021-43802 affects etherpad. Severity is critical (CVSS 9.9). Etherpad is a real-time collaborative editor. In versions prior to 1.8.16, an attacker can craft an `*.etherpad` file that, when imported, might allow the attacker to gain admin privileges for the Etherpad instance. This, in turn, can be us

How urgent is CVE-2021-43802?

Priority 55/100. Critical severity

Related CVEs

CVE-2021-34817 MEDIUM 6.1 DOWNGRADE A Cross-Site Scripting (XSS) issue in the chat component of Etherpad 1.8.13 allows remote attackers to inject
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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