Vulnerability Name:

CVE-2021-21394 (CCN-200111)

Assigned:2020-12-22
Published:2021-04-12
Updated:2021-11-23
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 1.28.0 Synapse is missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. Note that the groups feature is not part of the Matrix specification and the chosen maximum lengths are arbitrary. Not all clients might abide by them. Refer to referenced GitHub security advisory for additional details including workarounds.
CVSS v3 Severity:6.5 Medium (CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
5.7 Medium (Temporal CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C)
Exploitability Metrics:Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): None
Scope:Scope (S): Unchanged
Impact Metrics:Confidentiality (C): None
Integrity (I): None
Availibility (A): High
7.5 High (CCN CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
6.5 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:H/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): High
CVSS v2 Severity:4.0 Medium (CVSS v2 Vector: AV:N/AC:L/Au:S/C:N/I:N/A:P)
Exploitability Metrics:Access Vector (AV): Network
Access Complexity (AC): Low
Authentication (Au): Single_Instance
Impact Metrics:Confidentiality (C): None
Integrity (I): None
Availibility (A): Partial
7.8 High (CCN CVSS v2 Vector: AV:N/AC:L/Au:N/C:N/I:N/A:C)
Exploitability Metrics:Access Vector (AV): Network
Access Complexity (AC): Low
Athentication (Au): None
Impact Metrics:Confidentiality (C): None
Integrity (I): None
Availibility (A): Complete
Vulnerability Type:CWE-20
CWE-20
Vulnerability Consequences:Denial of Service
References:Source: MITRE
Type: CNA
CVE-2021-21394

Source: XF
Type: UNKNOWN
synapse-cve202121394-dos(200111)

Source: MISC
Type: Patch, Third Party Advisory
https://github.com/matrix-org/synapse/pull/9321

Source: MISC
Type: Patch, Third Party Advisory
https://github.com/matrix-org/synapse/pull/9393

Source: CCN
Type: Synapse GIT Repository
Denial of service (via resource exhaustion) due to improper input validation on third-party identifier endpoints

Source: CONFIRM
Type: Patch, Third Party Advisory
https://github.com/matrix-org/synapse/security/advisories/GHSA-w9fg-xffh-p362

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

Source: MISC
Type: Product, Third Party Advisory
https://pypi.org/project/matrix-synapse/

Vulnerable Configuration:Configuration 1:
  • cpe:/a:matrix:synapse:*:*:*:*:*:*:*:* (Version > 0.17.0 and < 1.28.0)

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

    • Configuration CCN 1:
  • cpe:/a:matrix:synapse:1.27.0:-:*:*:*:*:*:*

    • * Denotes that component is vulnerable
    BACK
    matrix synapse *
    fedoraproject fedora 34
    matrix synapse 1.27.0 -