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CVE-2021-21404

Published: 6 April 2021

Syncthing is a continuous file synchronization program. In Syncthing before version 1.15.0, the relay server `strelaysrv` can be caused to crash and exit by sending a relay message with a negative length field. Similarly, Syncthing itself can crash for the same reason if given a malformed message from a malicious relay server when attempting to join the relay. Relay joins are essentially random (from a subset of low latency relays) and Syncthing will by default restart when crashing, at which point it's likely to pick another non-malicious relay. This flaw is fixed in version 1.15.0.

Priority

Medium

Cvss 3 Severity Score

7.5

Score breakdown

Status

Package Release Status
syncthing
Launchpad, Ubuntu, Debian
bionic Needed

focal Needed

groovy Ignored
(end of life)
hirsute Ignored
(end of life)
impish Ignored
(end of life)
jammy Needed

kinetic Ignored
(end of life, was needed)
lunar Ignored
(end of life, was needed)
mantic Needed

trusty Does not exist

upstream Needs triage

xenial Does not exist

Severity score breakdown

Parameter Value
Base score 7.5
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H