Vulnerability Name:

CVE-2021-21392 (CCN-200109)

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 requests to user provided domains were not restricted to external IP addresses when transitional IPv6 addresses were used. Outbound requests to federation, identity servers, when calculating the key validity for third-party invite events, sending push notifications, and generating URL previews are affected. This could cause Synapse to make requests to internal infrastructure on dual-stack networks. See referenced GitHub security advisory for details and workarounds.
CVSS v3 Severity:6.3 Medium (CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N)
5.5 Medium (Temporal CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N/E:U/RL:O/RC:C)
Exploitability Metrics:Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): Required
Scope:Scope (S): Unchanged
Impact Metrics:Confidentiality (C): Low
Integrity (I): High
Availibility (A): None
6.5 Medium (CCN CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N)
5.7 Medium (CCN Temporal CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/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): Low
Integrity (I): Low
Availibility (A): None
CVSS v2 Severity:4.9 Medium (CVSS v2 Vector: AV:N/AC:M/Au:S/C:P/I:P/A:N)
Exploitability Metrics:Access Vector (AV): Network
Access Complexity (AC): Medium
Authentication (Au): Single_Instance
Impact Metrics:Confidentiality (C): Partial
Integrity (I): Partial
Availibility (A): None
6.4 Medium (CCN CVSS v2 Vector: AV:N/AC:L/Au:N/C:P/I:P/A:N)
Exploitability Metrics:Access Vector (AV): Network
Access Complexity (AC): Low
Athentication (Au): None
Impact Metrics:Confidentiality (C): Partial
Integrity (I): Partial
Availibility (A): None
Vulnerability Type:CWE-601
CWE-601
Vulnerability Consequences:Bypass Security
References:Source: MITRE
Type: CNA
CVE-2021-21392

Source: XF
Type: UNKNOWN
synapse-cve202121392-sec-bypass(200109)

Source: MISC
Type: Patch, Third Party Advisory
https://github.com/matrix-org/synapse/pull/9240

Source: CCN
Type: Synapse GIT Repository
IP blacklist bypass via transitional IPv6 addresses on dual-stack networks

Source: CONFIRM
Type: Patch, Third Party Advisory
https://github.com/matrix-org/synapse/security/advisories/GHSA-5wrh-4jwv-5w78

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 < 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 -