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CVE-2025-66622

matrix-sdk-base is vulnerable to DoS via custom m.room.join_rules event values

1.3 LowFix available

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

0.41%Up 0.4 points since Dec 9, 2025
90%50%10%1%

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 LowCVSS: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 LowCVSS: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 LowCVSS: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 LowCVSS: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 HighCVSS: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 LowCVSS: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 LowCVSS: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

Affected packages
PackageAffectedFixed
matrix-sdk-base
crates.io
before 0.16.0
0.16.0
matrix-sdk-base
crates.io
0.0.0-0 up to 0.16.0
0.16.0

History

History
RecordedChangedSources
factsOSV
first indexedCVE 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

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