CVE-2021-42612: A use after free in cleanup_index in index.c in Halibut 1.2 allows an attacker to cause a segmentation fault o

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HIGH 7.8DOWNGRADEMITIGATE

CVE-2021-42612 is a high-severity flaw (CVSS 7.8) affecting halibut, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A use after free in cleanup_index in index.c in Halibut 1.2 allows an attacker to cause a segmentation fault or possibly have other unspecified impact via a crafted text document.

Why this priority

High severity
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-416
Published	2022-05-24
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · halibut project

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

Am I affected?

Timeline

2022-05-24 19:15 UTCPublished CVE record published
2026-06-17 04:09 UTCUpdated Record last modified

halibut project halibut DOWNGRADE

Affected: 1.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.2

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.2 (Debian / Ubuntu)

apt-cache madison halibut sudo apt install halibut=<VERSION_BEFORE_1.2> sudo apt-mark hold halibut

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list halibut sudo dnf downgrade halibut-<VERSION_BEFORE_1.2> sudo dnf versionlock add halibut

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.

fedoraproject fedora MITIGATE

Affected: 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 35

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2021-42612?

halibut: downgrade or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-42612 being exploited?

CVE-2021-42612 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-2021-42612 affect?

CVE-2021-42612 affects halibut, fedora. Severity is high (CVSS 7.8). A use after free in cleanup_index in index.c in Halibut 1.2 allows an attacker to cause a segmentation fault or possibly have other unspecified impact via a crafted text document.

How urgent is CVE-2021-42612?

Priority 47/100. High severity; Public exploit reference

Related CVEs

CVE-2021-42614 HIGH 7.8 DOWNGRADE MITIGATE A use after free in info_width_internal in bk_info.c in Halibut 1.2 allows an attacker to cause a segmentation
CVE-2021-42613 HIGH 7.8 DOWNGRADE MITIGATE A double free in cleanup_index in index.c in Halibut 1.2 allows an attacker to cause a denial of service or po
CVE-2021-31819 CRITICAL 9.8 UPGRADE In Halibut versions prior to 4.4.7 there is a deserialisation vulnerability that could allow remote code execu

References

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