5.9

CVE-2021-40824: matrix element Authentication Bypass by Spoofing

CVSS: 5.9v3.1MediumModified
AliasesGHSA-jjmc-4p83-pp26
Published 13-09-2021Last modified 04-08-2024
Open JSON

Vulnerability summary

CVE-2021-40824 is a medium (CVSS 5.9) Authentication Bypass by Spoofing vulnerability in matrix element. EPSS estimates a 0.66% chance of exploitation in the next 30 days, higher than 50.6% of scored vulnerabilities.

Overall risk
24/100
0100
Low · default modelHow is this calculated?
CVSS score
5.9/10
010
Medium · v3.1 (NVD)
EPSS score
0.66%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 13-09-2021
    PublishedVulnerability first disclosed.
  2. 04-08-2024
    Last modifiedVulnerability information updated.

Description

A logic error in the room key sharing functionality of Element Android before 1.2.2 and matrix-android-sdk2 (aka Matrix SDK for Android) before 1.2.2 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 attacker to decrypt end-to-end encrypted messages sent by affected clients.

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

0.66%

Chance of exploitation in the next 30 days

Percentile

51%

Versus all other CVEs

30-day change

0.00 pp

From 0.66% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.66%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Matrix2 products
Org.matrix.android1 product
  • matrix-android-sdk2< 1.2.2

2 vendors · 3 products

References

3 links