CVE-2011-0520
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 · uneditedThe compress_add_dlabel_points function in dns/Compress.c in MaraDNS 1.4.03, 1.4.05, and probably other versions allows remote attackers to cause a denial of service (segmentation fault) and possibly execute arbitrary code via a long DNS hostname with a large number of labels, which triggers a heap-based buffer overflow.
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 confidenceHeap-based buffer overflow in the compress_add_dlabel_points function in MaraDNS's Compress.c allows remote attackers to cause denial of service or possibly execute arbitrary code by sending DNS queries with hostnames containing a large number of labels.
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= 1.4.03= 1.4.05CVSS 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 MaraDNS installation and versionCheck if MaraDNS is installed by looking for the executable (e.g., 'which maradns' or 'which dns'), or check installed packages. Query the DNS server for its version if possible, or check the binary/package version using your system's package manager.Affected if The installed MaraDNS version is 1.4.03 or 1.4.05 exactly, or if the exact version cannot be determined but falls within the 1.4.x range and matches the affected versions.
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Verify MaraDNS service is runningCheck if MaraDNS is actively running as a DNS service. Use commands like 'ps aux | grep -i mara' or check if DNS port 53 is listening (e.g., 'netstat -tlnp | grep :53' or 'ss -tlnp | grep :53').Affected if MaraDNS is running and listening on DNS ports (typically port 53 UDP/TCP), making it exposed to network queries.
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Confirm the vulnerable compression function existsInspect the Compress.c source file if accessible, or check the binary for the compress_add_dlabel_points function symbol. If MaraDNS is compiled from source, verify the presence of the vulnerable code path in the Compress.c file.Affected if The compress_add_dlabel_points function is present in the MaraDNS build and is used during DNS hostname compression operations.
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Assess network exposureDetermine if the MaraDNS instance is reachable from network locations. Check firewall rules, bind address configuration in MaraDNS config (typically csv4 or json format), and whether the service is bound to public IPs versus localhost only.Affected if The MaraDNS DNS service is accessible from untrusted networks, allowing remote attackers to send specially crafted DNS queries with many labels.
You are affected if MaraDNS version 1.4.03 or 1.4.05 is running and accessible on the network, enabling remote attackers to trigger the heap overflow via DNS queries with hostnames containing many labels.
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 dataUpdate MaraDNS to a patched version that properly bounds-checks the hostname compression logic, or implement DNS query filtering at network perimeter to reject unusually long or label-heavy DNS names.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-0520 — 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-2011-0520 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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