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Vulnerability · Published Sep 13, 2021 · Assigned by mitre

CVE-2021-40823

Medium 5.9

In plain English

A medium-severity security flaw in the element-web package (Alpine). There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS NVD)5.9Medium
Exploit odds (30 days)0.7%top 48.1% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20element-web1.8.4-r0ALPINE-CVE-2021-40823
Alpine:v3.21element-web1.8.4-r0ALPINE-CVE-2021-40823
Alpine:v3.22element-web1.8.4-r0ALPINE-CVE-2021-40823
Alpine:v3.23element-web1.8.4-r0ALPINE-CVE-2021-40823
Alpine:v3.24element-web1.8.4-r0ALPINE-CVE-2021-40823
Ubuntu:22.04:LTSnode-matrix-js-sdkno fix listedUBUNTU-CVE-2021-40823
Ubuntu:24.04:LTSnode-matrix-js-sdkno fix listedUBUNTU-CVE-2021-40823
npmmatrix-js-sdk12.4.1GHSA-23cm-x6j7-6hq3

Affected products (as reported)

VendorProductVersions
n/a n/a n/a

References