CVE-2021-36089: Grok 7.6.6 through 9.2.0 has a heap-based buffer overflow in grk::FileFormatDecompress::apply_palette_clr (cal

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HIGH 7.8UPGRADE

CVE-2021-36089 is a high-severity flaw (CVSS 7.8) affecting grok. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Grok 7.6.6 through 9.2.0 has a heap-based buffer overflow in grk::FileFormatDecompress::apply_palette_clr (called from grk::FileFormatDecompress::applyColour).

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.2% (top 32%)
CISA exploited list	No
Weakness	CWE-787
Published	2021-07-01
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: zope

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

Am I affected?

Timeline

2021-07-01 03:15 UTCPublished CVE record published
2026-06-17 03:58 UTCUpdated Record last modified

zope grok UPGRADE

Affected: >= 7.6.6 and <= 9.2.0

Fixed in: newer than 9.2.0

Safe to downgrade to: a release before 7.6.6

1. Check installed version

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

2. UPGRADE to newer than 9.2.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade grok

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 7.6.6 (Debian / Ubuntu)

apt-cache madison grok sudo apt install grok=<VERSION_BEFORE_7.6.6> sudo apt-mark hold grok

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

dnf --showduplicates list grok sudo dnf downgrade grok-<VERSION_BEFORE_7.6.6> sudo dnf versionlock add grok

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-2021-36089?

grok: upgrade to newer than 9.2.0. Exact commands for each OS are on this page.

Is CVE-2021-36089 being exploited?

CVE-2021-36089 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-2021-36089 affect?

CVE-2021-36089 affects grok. Severity is high (CVSS 7.8). Grok 7.6.6 through 9.2.0 has a heap-based buffer overflow in grk::FileFormatDecompress::apply_palette_clr (called from grk::FileFormatDecompress::applyColour).

How urgent is CVE-2021-36089?

Priority 49/100. High severity; Public exploit reference

Related CVEs

CVE-2021-45935 MEDIUM 5.5 DOWNGRADE Grok 9.5.0 has a heap-based buffer overflow in openhtj2k::T1OpenHTJ2K::decompress (called from std::__1::__pac

References

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