CVE-2021-29430
A malicious user could send an HTTP request with a very large body, leading to memory exhaustion and denial of service.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.83%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Sydent is a reference Matrix identity server. Sydent does not limit the size of requests it receives from HTTP clients. A malicious user could send an HTTP request with a very large body, leading to memory exhaustion and denial of service. Sydent also does not limit response size for requests it makes to remote Matrix homeservers. A malicious homeserver could return a very large response, again leading to memory exhaustion and denial of service. This affects any server which accepts registration requests from untrusted clients. This issue has been patched by releases 89071a1, 0523511, f56eee3. As a workaround request sizes can be limited in an HTTP reverse-proxy. There are no known workarounds for the problem with overlarge responses.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 1.83% probability · 78th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-20, CWE-400, CWE-770
- Affected
- matrix/sydent
- Source
- security-advisories@github.com
References
- https://github.com/matrix-org/sydent/commit/0523511d2fb40f2738f8a8549868f44b96e5dab7Patch, Third Party Advisory
- https://github.com/matrix-org/sydent/commit/89071a1a754c69a50deac89e6bb74002d4cda19dPatch, Third Party Advisory
- https://github.com/matrix-org/sydent/commit/f56eee315b6c44fdd9f6aa785cc2ec744a594428Patch, Third Party Advisory
- https://github.com/matrix-org/sydent/releases/tag/v2.3.0Release Notes, Third Party Advisory
- https://github.com/matrix-org/sydent/security/advisories/GHSA-wmg4-8cp2-hpg9Patch, Third Party Advisory
- https://pypi.org/project/matrix-sydent/Product, Third Party Advisory
- https://github.com/matrix-org/sydent/commit/0523511d2fb40f2738f8a8549868f44b96e5dab7Patch, Third Party Advisory
- https://github.com/matrix-org/sydent/commit/89071a1a754c69a50deac89e6bb74002d4cda19dPatch, Third Party Advisory
- https://github.com/matrix-org/sydent/commit/f56eee315b6c44fdd9f6aa785cc2ec744a594428Patch, Third Party Advisory
- https://github.com/matrix-org/sydent/releases/tag/v2.3.0Release Notes, Third Party Advisory
- https://github.com/matrix-org/sydent/security/advisories/GHSA-wmg4-8cp2-hpg9Patch, Third Party Advisory
- https://pypi.org/project/matrix-sydent/Product, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.