CVE-2003-0843
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedFormat 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFormat string vulnerability in mod_gzip_printf function in mod_gzip 1.3.26.1a and earlier allows remote attackers to execute arbitrary code via format string characters in HTTP GET requests containing 'Accept-Encoding: gzip' headers when debug mode is enabled with Apache logging.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 1.3.26.1aCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/C:P/I:P/A:P
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify if mod_gzip is loaded in ApacheCheck your Apache configuration files (httpd.conf, apache2.conf, or included module config files) for lines containing 'LoadModule gzip_module' or 'LoadModule mod_gzip'. Alternatively, run 'apachectl -M' or 'httpd -M' to list loaded modules and search for 'gzip'.Affected if mod_gzip is loaded as a module in the Apache server
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Determine the installed mod_gzip versionCheck the mod_gzip source files or RPM package if installed via a package manager. For RPM-based systems, run 'rpm -qi mod_gzip' or 'rpm -qa | grep -i gzip'. For Debian-based systems, check the package version. If built from source, inspect the version in the source files or the compiled module.Affected if The version is 1.3.26.1a or any earlier version
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Verify if debug mode is enabled in mod_gzip configurationSearch Apache configuration files for 'mod_gzip' directives, specifically looking for 'mod_gzip_debug' or similar debug-related settings. Common config locations: httpd.conf, apache2.conf, or separate mod_gzip.conf in conf.d or mods-enabled directories.Affected if Debug mode directives are present and set to on/enabled in the active Apache configuration
The environment is affected if mod_gzip version 1.3.26.1a or earlier is loaded AND debug mode is enabled in the Apache configuration, allowing the format string vulnerability to be exploited via crafted Accept-Encoding headers.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade from mod_gzip to mod_deflate (standard in Apache 2.x) or apply vendor patches; immediately disable debug mode in production if upgrade is not feasible.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2003-0843 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2003-0843 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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