PT-2021-14481 · Syncthing+2 · Syncthing+2

Wojciech Paciorek · Published 2021-04-06 · Updated 2024-08-21 · CVE-2021-21404

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

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

Name of the Vulnerable Software and Affected Versions Syncthing versions prior to 1.15.0

Description The issue allows a malicious relay server to cause Syncthing to crash by sending a malformed relay protocol message with a negative length field. Similarly, the relay server strelaysrv can be crashed by sending such a message. This can happen when Syncthing attempts to join a relay and is given a malformed message. It's noted that sensitive data is not exposed due to this issue, and Syncthing would need to be connected to a malicious relay server to exploit it.

Recommendations For Syncthing versions prior to 1.15.0, update to version 1.15.0 to resolve the issue. As a temporary workaround, consider configuring Syncthing to not use relays, or to only use specific, trusted relays, to minimize the risk of exploitation.

Fix

RCE

Weakness Enumeration

CWE-20

Related Identifiers

ALT-PU-2021-2071

ALT-PU-2021-2113

ALT-PU-2024-3833

BIT-SYNCTHING-2021-21404

CVE-2021-21404

GHSA-X462-89PF-6R5H

GO-2022-0888

OPENSUSE-SU-2021:0688-1

OPENSUSE-SU-2021:0713-1

OPENSUSE-SU-2021_0688-1

OPENSUSE-SU-2024:11417-1

Affected Products

Alt Linux

Suse

Syncthing

References · 21

• https://github.com/syncthing/syncthing/commit/fb4fdaf4c0a79c22cad000c42ac1394e3ccb6a97 · Patch
• https://osv.dev/vulnerability/GHSA-x462-89pf-6r5h · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-21404 · Vendor Advisory
• https://osv.dev/vulnerability/GO-2022-0888 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2021:0688-1 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2021-21404 · Security Note
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-21404 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-21404 · Security Note
• https://osv.dev/vulnerability/openSUSE-SU-2024:11417-1 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2021:0713-1 · Vendor Advisory
• https://ubuntu.com/security/CVE-2021-21404 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2021-21404 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-21404 · Vendor Advisory
• https://osv.dev/vulnerability/BIT-syncthing-2021-21404 · Vendor Advisory
• https://github.com/syncthing/syncthing/security/advisories/GHSA-x462-89pf-6r5h · Note