PT-2021-14471 · Matrix+1 · Synapse+1

Mscherer + 1 · Published 2021-02-25 · Updated 2021-11-23 · CVE-2021-21392

Positive Technologies (AI Summary)

CVSS v4.0

7.1

High

Base vector

AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N

Name of the Vulnerable Software and Affected Versions Synapse versions prior to 1.28.0

Description The issue affects Synapse, a Matrix reference homeserver written in python, where requests to user-provided domains were not restricted to external IP addresses when transitional IPv6 addresses were used. This could cause Synapse to make requests to internal infrastructure on dual-stack networks, affecting outbound requests to federation, identity servers, key validity calculations for third-party invite events, push notifications, and URL previews.

Recommendations For Synapse versions prior to 1.28.0, update to version 1.28.0 or later to resolve the issue. As a temporary workaround, consider blocking outbound requests to the following address ranges by a firewall, if unused for internal communication between systems: ::ffff/80, ::0000/80, and 2002::/16.

Fix

Open Redirect

Weakness Enumeration

CWE-601

Related Identifiers

ALT-PU-2021-1402

CVE-2021-21392

GHSA-5WRH-4JWV-5W78

PYSEC-2021-25

Affected Products

Alt Linux

Synapse

References · 20

• https://github.com/matrix-org/synapse/security/advisories/GHSA-5wrh-4jwv-5w78 · Patch
• https://github.com/matrix-org/synapse/pull/9240 · Patch
• https://security-tracker.debian.org/tracker/CVE-2021-21392 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-21392 · Security Note
• https://ubuntu.com/security/CVE-2021-21392 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-21392 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-5wrh-4jwv-5w78 · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/[e-mail]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2021-21392 · Security Note
• https://osv.dev/vulnerability/CVE-2021-21392 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-21392 · Vendor Advisory
• https://osv.dev/vulnerability/PYSEC-2021-25 · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY · Vendor Advisory
• https://github.com/matrix-org/synapse/commit/4ca054a4eaa714d0befb4fc30b19a1131e52c9cc · Note
• https://github.com/matrix-org/synapse · Note