CVE-2021-29430: Sydent vulnerable to denial of service attack via memory exhaustion

CVE-2021-29430 · Severity: low · CVSS 3.1 · Published 2021-04-15

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.

Technologies: matrix-sydent (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2021-29430 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2021-29430 being exploited in the wild.
How severe is CVE-2021-29430?
Low severity, with a CVSS score of 3.1, published 15 April 2021.
Which products and versions are affected?
matrix-sydent (PyPI) ECOSYSTEM:introduced=0,fixed=2.3.0, GIT:introduced=0,fixed=0523511d2fb40f2738f8a8549868f44b96e5dab7,fixed=89071a1a754c69a50deac89e6bb74002d4cda19d,fixed=f56eee315b6c44fdd9f6aa785cc2ec744a594428|ECOSYSTEM:introduced=0,fixed=2.3.0.
Is there a fix for CVE-2021-29430?
Yes. matrix-sydent (PyPI): upgrade to 2.3.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2021-29430?
Check whether you run matrix-sydent (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • matrix-sydent (PyPI): upgrade to 2.3.0 or later
    pip install "matrix-sydent>=2.3.0"

Affected products

  • matrix-sydent (PyPI) ECOSYSTEM:introduced=0,fixed=2.3.0, GIT:introduced=0,fixed=0523511d2fb40f2738f8a8549868f44b96e5dab7,fixed=89071a1a754c69a50deac89e6bb74002d4cda19d,fixed=f56eee315b6c44fdd9f6aa785cc2ec744a594428|ECOSYSTEM:introduced=0,fixed=2.3.0

Identifiers

  • CVE-2021-29430
  • GHSA-wmg4-8cp2-hpg9
  • PYSEC-2021-21

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