PT-2021-14473 · Synapse+1 · Synapse+1

Richvdh · Published 2021-02-25 · Updated 2021-11-23 · CVE-2021-21394

Positive Technologies (AI Summary)

CVSS v3.1

6.5

Medium

Base vector

AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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

Description The issue is caused by missing input validation of some parameters on the endpoints used to confirm third-party identifiers, which could lead to excessive use of disk space and memory, resulting in resource exhaustion. The affected endpoints include "/ matrix/client/(r0|unstable)/register/email", "/ matrix/client/(r0|unstable)/register/msisdn", "/ matrix/client/(r0|unstable)/account/password", and "/ matrix/client/(r0|unstable)/account/3pid".

Recommendations For versions prior to 1.28.0, consider the following workarounds:

1. Disable using email as third-party identifiers by not configuring the email setting.
2. Disable using phone numbers as third-party identifiers by ensuring that account threepid delegates.msisdn is not configured.
3. Block the affected endpoint patterns at a reverse proxy, including "^/ matrix/client/(r0|unstable)/register/email", "^/ matrix/client/(r0|unstable)/register/msisdn", "^/ matrix/client/(r0|unstable)/account/password", and "^/ matrix/client/(r0|unstable)/account/3pid". Update to version 1.28.0 or later to fix the issue.

Fix

RCE

Weakness Enumeration

CWE-20

Related Identifiers

ALT-PU-2021-1402

CVE-2021-21394

GHSA-W9FG-XFFH-P362

PYSEC-2021-27

Affected Products

Alt Linux

Synapse

References · 19

• https://github.com/matrix-org/synapse/pull/9321 · Patch
• https://github.com/matrix-org/synapse/pull/9393 · Patch
• https://github.com/matrix-org/synapse/security/advisories/GHSA-w9fg-xffh-p362 · Patch
• https://security-tracker.debian.org/tracker/CVE-2021-21394 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-21394 · Security Note
• https://lists.fedoraproject.org/archives/list/[e-mail]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2021-21394 · Security Note
• https://ubuntu.com/security/CVE-2021-21394 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-w9fg-xffh-p362 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2021-21394 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-21394 · Vendor Advisory
• https://osv.dev/vulnerability/PYSEC-2021-27 · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-21394 · Vendor Advisory
• https://github.com/matrix-org/synapse · Note