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.
Published 2021-04-15 21:15:17
Updated 2022-08-03 10:13:56
Source GitHub, Inc.
View at NVD,   CVE.org
Vulnerability category: Input validationDenial of service

Exploit prediction scoring system (EPSS) score for CVE-2021-29430

0.47%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 73 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2021-29430

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
5.0
MEDIUM AV:N/AC:L/Au:N/C:N/I:N/A:P
10.0
2.9
NIST
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.9
3.6
NIST
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.9
3.6
GitHub, Inc.

CWE ids for CVE-2021-29430

  • The 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.
    Assigned by: security-advisories@github.com (Secondary)
  • The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
    Assigned by: security-advisories@github.com (Secondary)
  • The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.
    Assigned by: nvd@nist.gov (Primary)

References for CVE-2021-29430

Products affected by CVE-2021-29430

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