CVE-2021-43802Network attack vector

Administrator escalation via arbitrary database record overwrite

Published Dec 9, 2021 · Updated Aug 4, 2024

Improper input validation in Etherpad before 1.8.16 allows remote authenticated users to gain administrator privileges via a crafted import. The import handler writes records from an .etherpad file without restricting their keys to the target pad, allowing non-pad database records to be overwritten. Exploitation requires reuse of a signed session cookie after its express-session state is deleted, and administrator access permits malicious plugin installation and server-side command execution.

CVSS severity9.9
Critical
EPSS probability1.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Etherpad before 1.8.16 allows remote authenticated users to gain administrator privileges via a crafted import. The import handler writes records from an .etherpad file without restricting their keys to the target pad, allowing non-pad database records to be overwritten. Exploitation requires reuse of a signed session cookie after its express-session state is deleted, and administrator access permits malicious plugin installation and server-side command execution.

The record

CVE
CVE-2021-43802
Published
Dec 9, 2021
Updated
Aug 4, 2024
Vendor
Etherpad Foundation
Product
Etherpad
Classifications
CWE-790, CWE-1287, CWE-20, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.8.16

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Etherpad Foundation · Etherpadversion=< 1.8.16

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C
9.9GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-790Improper Filtering of Special Elements
CWE-1287Improper Validation of Specified Type of Input
CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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