CVE-2023-29421: An issue was discovered in libbzip3.a in bzip3 before 1.2.3

Q: How do I fix CVE-2023-29421?

bzip3: upgrade to 1.2.3. Exact commands for each OS are on this page.

Q: Is CVE-2023-29421 being exploited?

CVE-2023-29421 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2023-29421 affect?

CVE-2023-29421 affects bzip3. Severity is high (CVSS 8.8). An issue was discovered in libbzip3.a in bzip3 before 1.2.3. There is an out-of-bounds write in bz3_decode_block.

Q: How urgent is CVE-2023-29421?

Priority 51/100. High severity; Public exploit reference

This month

HIGH 8.8UPGRADE

CVE-2023-29421 is a high-severity flaw (CVSS 8.8) affecting bzip3. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in libbzip3.a in bzip3 before 1.2.3. There is an out-of-bounds write in bz3_decode_block.

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-787
Published	2023-04-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: bzip3 project

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

Am I affected?

Timeline

2023-04-06 05:15 UTCPublished CVE record published
2026-06-17 05:50 UTCUpdated Record last modified

bzip3 project bzip3 UPGRADE

Affected: < 1.2.3

Fixed in: 1.2.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy bzip3 || rpm -q bzip3 || bzip3 --version

2. UPGRADE to 1.2.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bzip3

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bzip3

Note

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

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-2023-29421?

bzip3: upgrade to 1.2.3. Exact commands for each OS are on this page.

Is CVE-2023-29421 being exploited?

CVE-2023-29421 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-2023-29421 affect?

CVE-2023-29421 affects bzip3. Severity is high (CVSS 8.8). An issue was discovered in libbzip3.a in bzip3 before 1.2.3. There is an out-of-bounds write in bz3_decode_block.

How urgent is CVE-2023-29421?

Priority 51/100. High severity; Public exploit reference

Related CVEs

CVE-2023-29420 MEDIUM 6.5 UPGRADE An issue was discovered in libbzip3.a in bzip3 before 1.2.3
CVE-2023-29419 MEDIUM 6.5 UPGRADE An issue was discovered in libbzip3.a in bzip3 before 1.2.3
CVE-2023-29418 MEDIUM 6.5 UPGRADE An issue was discovered in libbzip3.a in bzip3 before 1.2.3
CVE-2023-29417 MEDIUM 6.5 DOWNGRADE An issue was discovered in libbzip3.a in bzip3 1.2.2
CVE-2023-29416 MEDIUM 6.5 UPGRADE An issue was discovered in libbzip3.a in bzip3 before 1.3.0

References

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