CVE-2021-21387: Partial secret key disclosure, improper safety number calculation, & inadequate encryption strength

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-19 · updated 2026-06-17
Weakness: CWE-319

Description

Wrongthink peer-to-peer, end-to-end encrypted messenger with PeerJS and Axolotl ratchet. In wrongthink from version 2.0.0 and before 2.3.0 there was a set of vulnerabilities causing inadequate encryption strength. Part of the secret identity key was disclosed by the fingerprint used for connection. Additionally, the safety number was improperly calculated. It was computed using part of one of the public identity keys instead of being derived from both public identity keys. This caused issues in computing safety numbers which would potentially be exploitable in the real world. Additionally there was inadequate encryption strength due to use of 1024-bit DSA keys. These issues are all fixed in version 2.3.0.

Affected products

parabirb wrongthink: from 2.0.0 before 2.3.0 — fixed in 2.3.0

How to fix

Upgrade to a fixed version: parabirb wrongthink 2.3.0. Check the vendor advisory for mitigations.

References

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