Vulnerability Name:

CVE-2021-29471 (CCN-201731)

Assigned:2021-05-11
Published:2021-05-11
Updated:2022-04-05
Summary: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.
CVSS v3 Severity:5.3 Medium (CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)
4.6 Medium (Temporal CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C)
Exploitability Metrics:Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope:Scope (S): Unchanged
Impact Metrics:Confidentiality (C): None
Integrity (I): None
Availibility (A): Low
5.3 Medium (CCN CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)
4.6 Medium (CCN Temporal CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C)
Exploitability Metrics:Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope:Scope (S): Unchanged
Impact Metrics:Confidentiality (C): None
Integrity (I): None
Availibility (A): Low
CVSS v2 Severity:5.0 Medium (CVSS v2 Vector: AV:N/AC:L/Au:N/C:N/I:N/A:P)
Exploitability Metrics:Access Vector (AV): Network
Access Complexity (AC): Low
Authentication (Au): None
Impact Metrics:Confidentiality (C): None
Integrity (I): None
Availibility (A): Partial
5.0 Medium (CCN CVSS v2 Vector: AV:N/AC:L/Au:N/C:N/I:N/A:P)
Exploitability Metrics:Access Vector (AV): Network
Access Complexity (AC): Low
Athentication (Au): None
Impact Metrics:Confidentiality (C): None
Integrity (I): None
Availibility (A): Partial
Vulnerability Type:CWE-331
Vulnerability Consequences:Denial of Service
References:Source: MITRE
Type: CNA
CVE-2021-29471

Source: XF
Type: UNKNOWN
matrix-cve202129471-dos(201731)

Source: MISC
Type: Patch, Third Party Advisory
https://github.com/matrix-org/synapse/commit/03318a766cac9f8b053db2214d9c332a977d226c

Source: MISC
Type: Release Notes, Third Party Advisory
https://github.com/matrix-org/synapse/releases/tag/v1.33.2

Source: CCN
Type: Synapse GIT Repository
Denial of service attack via push rule patterns

Source: CONFIRM
Type: Patch, Third Party Advisory
https://github.com/matrix-org/synapse/security/advisories/GHSA-x345-32rc-8h85

Source: FEDORA
Type: Mailing List, Third Party Advisory
FEDORA-2021-a627cfd31e

Vulnerable Configuration:Configuration 1:
  • cpe:/a:matrix:synapse:*:*:*:*:*:*:*:* (Version < 1.33.2)

    • Configuration 2:
  • cpe:/o:fedoraproject:fedora:34:*:*:*:*:*:*:*

    • * Denotes that component is vulnerable
    Oval Definitions
    Definition IDClassTitleLast Modified
    oval:org.opensuse.security:def:112972
    P
    		matrix-synapse-1.43.0-1.1 on GA media (Moderate)
    2022-01-17
    oval:org.opensuse.security:def:106421
    P
    		matrix-synapse-1.43.0-1.1 on GA media (Moderate)
    2021-10-01
    BACK
    matrix synapse *
    fedoraproject fedora 34