matrix-sdk-base denial of service via custom m.room.join_rules event values

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 https://github.com/matrix-org/matrix-rust-sdk/pull/5924.

Source published

8 Dec 2025 22:07:47 UTC

Source modified

9 Dec 2025 19:36:28 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

Publisher rating · LOW