5.3
MEDIUM
CVE-2021-29471
Matrix Synapse Denial-of-Service Vulnerability in Push Rules Pattern Matching
Description

Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.33.2 "Push rules" can specify conditions under which they will match, including `event_match`, which matches event content against a pattern including wildcards. Certain patterns can cause very poor performance in the matching engine, leading to a denial-of-service when processing moderate length events. The issue is patched in version 1.33.2. A potential workaround might be to prevent users from making custom push rules, by blocking such requests at a reverse-proxy.

INFO

Published Date :

May 11, 2021, 3:15 p.m.

Last Modified :

Nov. 7, 2023, 3:32 a.m.

Remotely Exploitable :

Yes !

Impact Score :

1.4

Exploitability Score :

3.9
Affected Products

The following products are affected by CVE-2021-29471 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Fedoraproject fedora
1 Matrix synapse
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2021-29471.

URL Resource
https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c Patch Third Party Advisory
https://github.com/matrix-org/synapse/releases/tag/v1.33.2 Release Notes Third Party Advisory
https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85 Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-29471 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2021-29471 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • CVE Modified by [email protected]

    Nov. 07, 2023

    Action Type Old Value New Value
    Added Reference GitHub, Inc. https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/ [No types assigned]
    Removed Reference GitHub, Inc. https://lists.fedoraproject.org/archives/list/[email protected]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/
  • Modified Analysis by [email protected]

    Apr. 05, 2022

    Action Type Old Value New Value
    Changed Reference Type https://lists.fedoraproject.org/archives/list/[email protected]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/ No Types Assigned https://lists.fedoraproject.org/archives/list/[email protected]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/ Mailing List, Third Party Advisory
    Added CWE NIST CWE-331
    Added CPE Configuration OR *cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
  • CVE Modified by [email protected]

    Aug. 02, 2021

    Action Type Old Value New Value
    Added Reference https://lists.fedoraproject.org/archives/list/[email protected]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/ [No Types Assigned]
  • Initial Analysis by [email protected]

    May. 25, 2021

    Action Type Old Value New Value
    Added CVSS V2 NIST (AV:N/AC:L/Au:N/C:N/I:N/A:P)
    Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
    Changed Reference Type https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c No Types Assigned https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c Patch, Third Party Advisory
    Changed Reference Type https://github.com/matrix-org/synapse/releases/tag/v1.33.2 No Types Assigned https://github.com/matrix-org/synapse/releases/tag/v1.33.2 Release Notes, Third Party Advisory
    Changed Reference Type https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85 No Types Assigned https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85 Patch, Third Party Advisory
    Added CPE Configuration OR *cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:* versions up to (excluding) 1.33.2
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-29471 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

0.15 }} 0.02%

score

0.51705

percentile

CVSS31 - Vulnerability Scoring System
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Attack Complexity
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Scope
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