# CVE-2021-21404: GO-2022-0888 - Crash due to malformed relay protocol message in github.com/syncthing/syncthing

Source: https://junglewise.ai/threats/cve-2021-21404-crash-due-to-malformed-relay-protocol-message  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2024-08-21  
License: CC BY 4.0 with a link back

CVE-2021-21404 · Severity: low · CVSS 3.1 · Published 2024-08-21

Crash due to malformed relay protocol message in github.com/syncthing/syncthing

Technologies: [github.com/syncthing/syncthing (Go)](https://junglewise.ai/threats/technologies/github-com-syncthing-syncthing). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2021-21404 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-21404 being exploited in the wild.

**How severe is CVE-2021-21404?** Low severity, with a CVSS score of 3.1, published 21 August 2024.

**Which products and versions are affected?** github.com/syncthing/syncthing (Go) SEMVER:introduced=0,fixed=1.15.0.

**Is there a fix for CVE-2021-21404?** Yes. github.com/syncthing/syncthing (Go): upgrade to 1.15.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-21404?** Check whether you run github.com/syncthing/syncthing (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/syncthing/syncthing (Go): upgrade to 1.15.0 or later

  ```sh
  go get github.com/syncthing/syncthing@v1.15.0
  ```


## Affected products

- github.com/syncthing/syncthing (Go) SEMVER:introduced=0,fixed=1.15.0

## Identifiers

- CVE-2021-21404
- GHSA-x462-89pf-6r5h
- GO-2022-0888

## Related threats

- [syncthing vulnerable to Cross-site Scripting (XSS) in Web GUI](https://junglewise.ai/threats/cve-2022-46165-syncthing-vulnerable-to-cross-site-scripting-xss-in-web-gui)
- [Syncthing vulnerable to symlink traversal and arbitrary file overwrite](https://junglewise.ai/threats/cve-2017-1000420-syncthing-vulnerable-to-symlink-traversal-and-arbitrary-file)