CVE-2006-4336: Buffer underflow in the build_tree function in unpack.c in gzip 1.3.5 allows context-dependent attackers to ex

This month

HIGH 7.5DOWNGRADE

CVE-2006-4336 is a high-severity flaw (CVSS 7.5) affecting gzip. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer underflow in the build_tree function in unpack.c in gzip 1.3.5 allows context-dependent attackers to execute arbitrary code via a crafted leaf count table that causes a write to a negative index.

Why this priority

High severity
EPSS top 7%: very likely to be exploited

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	6.0% (top 7%)
CISA exploited list	No
Published	2006-09-19
Last modified	2026-06-16

Publisher (CNA): Red Hat, Inc. · Vendor: gzip

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2006-09-19 21:07 UTCPublished CVE record published
2026-06-16 22:28 UTCUpdated Record last modified

gzip gzip DOWNGRADE

Affected: 1.3.5

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.3.5

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.3.5 (Debian / Ubuntu)

apt-cache madison gzip sudo apt install gzip=<VERSION_BEFORE_1.3.5> sudo apt-mark hold gzip

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

dnf --showduplicates list gzip sudo dnf downgrade gzip-<VERSION_BEFORE_1.3.5> sudo dnf versionlock add gzip

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-2006-4336?

gzip: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2006-4336 being exploited?

CVE-2006-4336 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-2006-4336 affect?

CVE-2006-4336 affects gzip. Severity is high (CVSS 7.5). Buffer underflow in the build_tree function in unpack.c in gzip 1.3.5 allows context-dependent attackers to execute arbitrary code via a crafted leaf count table that causes a write to a negative index.

How urgent is CVE-2006-4336?

Priority 50/100. High severity; EPSS top 7%: very likely to be exploited

Related CVEs

CVE-2026-41992 HIGH 7.5 UPGRADE GNU gzip contains a global buffer overflow vulnerability in the LZH decompression logic caused by improper reu
CVE-2026-41991 MEDIUM 4.7 UPGRADE GNU gzip contains a vulnerability in the gzexe utility related to insecure temporary file handling
CVE-2022-1271 HIGH 8.8 UPGRADE DOWNGRADE An arbitrary file write vulnerability was found in GNU gzip's zgrep utility
CVE-2010-0001 MEDIUM 6.8 UPGRADE Integer underflow in the unlzw function in unlzw.c in gzip before 1.4 on 64-bit platforms, as used in ncompres
CVE-2009-2624 MEDIUM 6.8 UPGRADE The huft_build function in inflate.c in gzip before 1.3.13 creates a hufts (aka huffman) table that is too sma

References

← Back to latest CVEs