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Security Advisories: GSA_kwCzR0hTQS0ycHZqLXA0ODUtY3Azbc4AAvIh
matrix-android-sdk2 vulnerable to impersonation via forwarded Megolm sessions
Impact
An attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others.
This attack is possible due to the matrix-android-sdk2 implementing a too permissive key forwarding strategy on the receiving end.
Key forwarding is a mechanism allowing clients to recover from “unable to decrypt” messages when they missed the initial key distribution, at the time the message was originally sent. Examples include accessing message history before they joined the room but also when some network/federation errors have occurred.
Patches
The default policy for accepting key forwards has been made more strict in the matrix-android-sdk2. The matrix-android-sdk2 will now only accept forwarded keys in response to previously issued requests and only from own, verified devices.
A unique exception to this rule is with the experimental MSC3061, that is forwarding room keys for past messages when invited in a room configured with the proper history visibility setting. Such key forwards are parked upon receipt and are only accepted if the SDK receives an invitation for that room from the inviter in a limited time window.
The SDK now sets a trusted
flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with trusted = false
are decorated appropriately (for example, by showing a warning for such messages).
Workarounds
Current users of the SDK can disable key forwarding in their forks using CryptoService#enableKeyGossiping(enable: Boolean)
.
References
For more information
If you have any questions or comments about this advisory, e-mail us at [email protected].
Permalink: https://github.com/advisories/GHSA-2pvj-p485-cp3mJSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS0ycHZqLXA0ODUtY3Azbc4AAvIh
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: about 2 years ago
Updated: almost 2 years ago
CVSS Score: 7.5
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS Percentage: 0.00103
EPSS Percentile: 0.43092
Identifiers: GHSA-2pvj-p485-cp3m, CVE-2022-39246
References:
- https://github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-2pvj-p485-cp3m
- https://nvd.nist.gov/vuln/detail/CVE-2022-39246
- https://github.com/matrix-org/matrix-spec-proposals/pull/3061
- 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/advisories/GHSA-2pvj-p485-cp3m
Blast Radius: 5.2
Affected Packages
maven:org.matrix.android:matrix-android-sdk2
Dependent packages: 0Dependent repositories: 5
Downloads:
Affected Version Ranges: <= 1.4.36
Fixed in: 1.5.1
All affected versions: 0.0.2, 1.2.1, 1.2.2, 1.3.0, 1.3.2, 1.3.4, 1.3.7, 1.3.8, 1.3.9, 1.3.10, 1.3.13, 1.3.14, 1.3.18, 1.4.2, 1.4.4, 1.4.11, 1.4.13, 1.4.14, 1.4.16, 1.4.25, 1.4.27, 1.4.32, 1.4.34, 1.4.36
All unaffected versions: 1.5.1, 1.5.2, 1.5.4, 1.5.7, 1.5.8, 1.5.11, 1.5.18, 1.5.20, 1.5.22, 1.5.25, 1.5.26, 1.5.30, 1.6.10