CVE-2003-0843: Format string vulnerability in mod_gzip_printf for mod_gzip 1.3.26.1a and earlier, and possibly later official

Q: How do I fix CVE-2003-0843?

mod gzip: upgrade to newer than 1.3.26.1a. Exact commands for each OS are on this page.

Q: Is CVE-2003-0843 being exploited?

CVE-2003-0843 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-2003-0843 affect?

CVE-2003-0843 affects mod gzip. Severity is high (CVSS 7.5). Format string vulnerability in mod_gzip_printf for mod_gzip 1.3.26.1a and earlier, and possibly later official versions, when running in debug mode and using the Apache log, allows remote attackers to execute arbitrary code via format strin

This month

HIGH 7.5UPGRADE

CVE-2003-0843 is a high-severity flaw (CVSS 7.5) affecting mod gzip. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Format string vulnerability in mod_gzip_printf for mod_gzip 1.3.26.1a and earlier, and possibly later official versions, when running in debug mode and using the Apache log, allows remote attackers to execute arbitrary code via format string characters in an HTTP GET request with an "Accept-Encoding: gzip" header.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	2.3% (top 17%)
CISA exploited list	No
Published	2003-11-17
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: dag apt repository

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

Am I affected?

Timeline

2003-11-17 05:00 UTCPublished CVE record published
2026-06-16 22:03 UTCUpdated Record last modified

dag apt repository mod gzip UPGRADE

Affected: <= 1.3.26.1a

Fixed in: newer than 1.3.26.1a

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.3.26.1a (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mod-gzip

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mod-gzip

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-2003-0843?

mod gzip: upgrade to newer than 1.3.26.1a. Exact commands for each OS are on this page.

Is CVE-2003-0843 being exploited?

CVE-2003-0843 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-2003-0843 affect?

CVE-2003-0843 affects mod gzip. Severity is high (CVSS 7.5). Format string vulnerability in mod_gzip_printf for mod_gzip 1.3.26.1a and earlier, and possibly later official versions, when running in debug mode and using the Apache log, allows remote attackers to execute arbitrary code via format strin

How urgent is CVE-2003-0843?

Priority 47/100. High severity

Related CVEs

CVE-2003-0844 HIGH 7.1 UPGRADE mod_gzip 1.3.26.1a and earlier, and possibly later official versions, when running in debug mode without the A
CVE-2003-0842 HIGH 7.5 DOWNGRADE Stack-based buffer overflow in mod_gzip_printf for mod_gzip 1.3.26.1a and earlier, and possibly later official

References

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