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

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	Ignored (end of life, was needed)
	noble	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

References

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