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Denial of service due to custom `m.room.join_rules` events

Low
poljar published GHSA-jj6p-3m75-g2p3 Dec 8, 2025

Package

cargo matrix-sdk-base (Rust)

Affected versions

< 0.16.0

Patched versions

0.16.0

Description

The matrix-sdk-base crate is unable to handle responses that include custom m.room.join_rules values due to a serialization bug.

This can be exploited to cause a denial-of-service condition, if a user is invited to a room with non-standard join rules, the crate's sync process will stall, preventing further processing for all rooms.

Patches

The issue is fixed in matrix-sdk-base 0.16.0.

Workarounds

Users can leave affected rooms on another client to mitigate the issue.

References

The issue was fixed in #5924.

Severity

Low

CVE ID

CVE-2025-66622

Weaknesses

No CWEs