CVE-2021-29430: matrix-org sydent Improper Input Validation

Vulnerability summary

CVE-2021-29430 is a high (CVSS 7.5) Improper Input Validation vulnerability in matrix-org sydent. EPSS estimates a 1.83% chance of exploitation in the next 30 days, higher than 78.5% of scored vulnerabilities.

Timeline

1. 15-04-2021
   PublishedVulnerability first disclosed.
2. 03-08-2024
   Last modifiedVulnerability information updated.

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.

• CWE-20Improper Input ValidationThe product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
• CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.