CVE Tools
Sign in

CVE-2021-40823

Published: Sep 13, 2021Updated: Nov 21, 2024 Sources: CVE List NVD GHSACWE-290
5.9MEDIUM
NVD MITRE
EPSS Score
0.7%
Top 51.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

A logic error in the room key sharing functionality of matrix-js-sdk (aka Matrix Javascript SDK) before 12.4.1 allows a malicious Matrix homeserver present in an encrypted room to steal room encryption keys (via crafted Matrix protocol messages) that were originally sent by affected Matrix clients participating in that room. This allows the homeserver to decrypt end-to-end encrypted messages sent by affected clients.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:HI:NA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:NIntegrity
None
A:NAvailability
None
Open in CVSS calculator →

Weaknesses

CWE-290

Affected Products

matrix
oss-project·GBaka javascript sdk, matrix irc bridge, synapse
javascript sdkLibraryLibrary
Communications / messaging-chat
npm
package-ecosystem
matrix-js-sdk
OSS Libraries
and 1 more affected products View all →

Exploitability

Official Patch Available
Is your org exposed to CVE-2021-40823?We can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

Click technique nodes for MITRE ATT&CK details · drag to pan · Ctrl/⌘ + scroll to zoom, or go fullscreen.

MITRE ATT&CK

1 technique
Initial Access
View detailed technique mapping

References

https://github.com/matrix-org/matrix-js-sdk/releases/tag/v12.4.1
github.com
https://matrix.org/blog/2021/09/13/vulnerability-disclosure-key-sharing
matrix.org
https://github.com/matrix-org/matrix-js-sdk/security/advisories/GHSA-23cm-x6j7-6hq3
github.com
and 3 more references View all →

Unlock Complete Vulnerability Intelligence

Get the full picture for CVE-2021-40823 and every CVE in our database. Create a free account — no credit card required.

Create Free Account
Plain-language analysis
Impact assessment and exploitation scenario in plain English
Attack graph visualization
Interactive attack path and kill chain mapping
Exploit details & PoC links
ExploitDB, Metasploit, GitHub PoCs with direct links
Nuclei scanner templates
Ready-to-use vulnerability scanner templates
Full remediation guide
Patch instructions, workarounds, and compliance impact
Interactive AI chat
Ask questions about this vulnerability in natural language
Related vulnerabilities
Semantically similar CVEs and attack patterns
REST API & MCP access
Integrate vulnerability data into your workflows