CVE-2025-66622
matrix-sdk-base is vulnerable to DoS via custom m.room.join_rules event values
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Passive
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
1.3
matrix-sdk-base is vulnerable to DoS via custom m.room.join_rules event values
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.
- Record
CVE-2025-66622- CVSS 4.0
- 1.3 Low
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 - Weakness
- CWE-755
- Updated
- 2026-11-02
EUVDEUVD-2025-201827
1.3
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.
- Record
EUVD-2025-201827- CVSS 4.0
- 1.3 Low
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 - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-jj6p-3m75-g2p3
1.3
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.
- Record
GHSA-jj6p-3m75-g2p3- CVSS 4.0
- 1.3 Low
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 - Weakness
- CWE-755
- Updated
- 2026-11-02
NVD
1.3
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.
- Record
CVE-2025-66622- CVSS 4.0
- 1.3 Low
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-755
- Updated
- 2026-11-02
OSV
1.3
matrix-sdk-base is vulnerable to DoS via custom m.room.join_rules event values
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.
- Record
CVE-2025-66622- CVSS 4.0
- 1.3 Low
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 - Weakness
- CWE-755
- Updated
- 2026-11-04
OSVGHSA-jj6p-3m75-g2p3
1.3
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.
- Record
GHSA-jj6p-3m75-g2p3- CVSS 4.0
- 1.3 Low
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 - Weakness
- CWE-755
- Updated
- 2026-11-02
OSVRUSTSEC-2025-0135 No score
matrix-sdk-base: Denial of service due to custom `m.room.join_rules` events
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.
- Record
RUSTSEC-2025-0135- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
matrix-sdk-basecrates.io |
before 0.16.0 | 0.16.0 |
matrix-sdk-basecrates.io |
0.0.0-0 up to 0.16.0 | 0.16.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| facts | OSV | |
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-66622 is a low vulnerability (CVSS 1.3) in Matrix Matrix-rust-sdk, published December 8, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. Fixed in matrix-sdk-base 0.16.0.
References
github.com/matrix-org/matrix-rust-sdk/security/advisories/GHSA-jj6p-3m75-g2p3
github.com/matrix-org/matrix-rust-sdk/pull/5924
github.com/matrix-org/matrix-rust-sdk/commit/4ea0418abefab2aa93f8851a4d39c723e703e6b0
rustsec.org/advisories/RUSTSEC-2025-0135.html
nvd.nist.gov/vuln/detail/CVE-2025-66622
github.com/advisories/GHSA-jj6p-3m75-g2p3
github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66622.json
github.com/matrix-org/matrix-rust-sdk
crates.io/crates/matrix-sdk-base