CVE-2021-21387: Wrongthink peer-to-peer, end-to-end encrypted messenger with PeerJS and Axolotl ratchet

Routine

HIGH 8.1UPGRADE

CVE-2021-21387 is a high-severity flaw (CVSS 8.1) affecting wrongthink. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 67%)
CISA exploited list	No
Weakness	CWE-319, CWE-326, CWE-358
Published	2021-03-19
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: wrongthink

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-03-19 16:15 UTCPublished CVE record published
2026-06-17 03:35 UTCUpdated Record last modified

wrongthink wrongthink UPGRADE

Affected: >= 2.0.0 and < 2.3.0

Fixed in: 2.3.0

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy wrongthink || rpm -q wrongthink || wrongthink --version

2. UPGRADE to 2.3.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade wrongthink

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade wrongthink

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison wrongthink sudo apt install wrongthink=<VERSION_BEFORE_2.0.0> sudo apt-mark hold wrongthink

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list wrongthink sudo dnf downgrade wrongthink-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add wrongthink

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-21387?

wrongthink: upgrade to 2.3.0. Exact commands for each OS are on this page.

Is CVE-2021-21387 being exploited?

CVE-2021-21387 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-21387 affect?

CVE-2021-21387 affects wrongthink. Severity is high (CVSS 8.1). 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 identit

How urgent is CVE-2021-21387?

Priority 37/100. High severity

Related CVEs

CVE-2021-29467 MEDIUM 6.1 UPGRADE Wrongthink is an encrypted peer-to-peer chat program

References

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