CVE-2021-37632: SuperMartijn642's Config Lib is a library used by a number of mods for the game Minecraft

This month

HIGH 8.1REMOTEUPGRADE

CVE-2021-37632 is a high-severity flaw (CVSS 8.1) affecting config lib. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

SuperMartijn642's Config Lib is a library used by a number of mods for the game Minecraft. The versions of SuperMartijn642's Config Lib between 1.0.4 and 1.0.8 are affected by a vulnerability and can be exploited on both servers and clients. Using SuperMartijn642's Config Lib, servers will send a packet to clients with the server's config values. In order to read `enum` values from the packet data, `ObjectInputStream#readObject` is used. `ObjectI

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	1.7% (top 23%)
CISA exploited list	No
Weakness	CWE-502
Published	2021-08-05
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: config lib project

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

Am I affected?

Timeline

2021-08-05 21:15 UTCPublished CVE record published
2026-06-17 04:00 UTCUpdated Record last modified

config lib project config lib UPGRADE

Affected: >= 1.0.4 and < 1.0.9

Fixed in: 1.0.9

Safe to downgrade to: a release before 1.0.4

1. Check installed version

apt-cache policy config-lib || rpm -q config-lib || config-lib --version

2. UPGRADE to 1.0.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade config-lib

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade config-lib

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 1.0.4 (Debian / Ubuntu)

apt-cache madison config-lib sudo apt install config-lib=<VERSION_BEFORE_1.0.4> sudo apt-mark hold config-lib

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

dnf --showduplicates list config-lib sudo dnf downgrade config-lib-<VERSION_BEFORE_1.0.4> sudo dnf versionlock add config-lib

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-2021-37632?

config lib: upgrade to 1.0.9. Exact commands for each OS are on this page.

Is CVE-2021-37632 being exploited?

CVE-2021-37632 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-2021-37632 affect?

CVE-2021-37632 affects config lib. Severity is high (CVSS 8.1). SuperMartijn642's Config Lib is a library used by a number of mods for the game Minecraft. The versions of SuperMartijn642's Config Lib between 1.0.4 and 1.0.8 are affected by a vulnerability and can be exploited on both servers and clients

How urgent is CVE-2021-37632?

Priority 53/100. High severity; Remotely exploitable, no login, no user action

References

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