CVE-2021-21404

Publication date 6 April 2021

Last updated 11 July 2025

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

7.5 · High

Score breakdown

Description

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.

Status

Package Ubuntu Release Status
syncthing 25.10 questing
Vulnerable
25.04 plucky Ignored end of life, was needed
24.10 oracular Ignored end of life, was needed
24.04 LTS noble
Vulnerable
23.10 mantic Ignored end of life, was needed
23.04 lunar Ignored end of life, was needed
22.10 kinetic Ignored end of life, was needed
22.04 LTS jammy
Vulnerable
21.10 impish Ignored end of life
21.04 hirsute Ignored end of life
20.10 groovy Ignored end of life
20.04 LTS focal
Vulnerable
18.04 LTS bionic
Vulnerable
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release

Severity score breakdown

Parameter Value
Base score 7.5 · High
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

Other references

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