CVE-2021-40824

mediumpriority · track · 24OT risk · elevatedEPSS 0.007 · 52 %ileEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.66% (52nd) EPSS

CVSS 4.3 · medium

Is it mine?

4 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · nvd · osv

EPSS · scored 2026-10-28

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

Technical severity, 0–10. One row per scoring source.

5.9

010

base score 0–10 · higher = more severe · hover a vector to decode

v2.04.3mediumAV:N/AC:M/Au:N/C:P/I:N/A:Nprimary · NVD / NIST USexploitability 8.6 · impact 2.9

v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:Nprimary · NVD / NIST USexploitability 2.2 · impact 3.6

v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:Nsecondary · OSV

v3.15.4mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-290USprimaryCWE-327US

affected products (4)

Products and version ranges known to be affected.

n/a n/a≤ n/aenisa_euvdEU
matrix element< 1.2.2nvdUScpe:2.3:a:matrix:element:*:*:*:*:*:*:*:*
matrix matrix-android-sdk2< 1.2.2nvdUScpe:2.3:a:matrix:matrix-android-sdk2:*:*:*:*:*:*:*:*
Maven org.matrix.android:matrix-android-sdk2< 1.2.2osvUSpkg:maven/org.matrix.android/matrix-android-sdk2

advisories (1)

Vendor and ecosystem advisories describing this.

GHSA-jjmc-4p83-pp26Logic error in Matrix SDK for Android2022-05-24ghsa · osvUS
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 leads to a situation where identity verification is inadequate and thus a key-requesting device can be impersonated.

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd osv NVD CVE.org MITRE

published 2021-09-13modified 2026-06-17

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references (9)

External citations — patches, advisories, analysis.

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