PyxmlApplication · Python
CVE-2012-0877
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 · uneditedPyXML: Hash table collisions CPU usage Denial of Service
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 · moderate confidencePyXML library contains a hash table collision vulnerability where specially crafted XML input with many attributes or elements that hash to the same value causes excessive CPU consumption, leading to denial of service. Attackers can exploit this by sending malicious XML documents that trigger O(n²) hash collision behavior.
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
PyxmlApplication
all versions
Enterprise Virtualization HypervisorApplication
all versions
Enterprise LinuxOperating system
= 5.0= 6.0CVSS 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
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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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Determine if PyXML is installedRun 'python -c "import pyxml; print(pyxml.__file__)" 2>/dev/null' or 'python -c "import xml"; print(xml.__file__)" 2>/dev/null' to locate the xml module. On Red Hat systems, also check 'rpm -qa | grep -i pyxml' or 'rpm -qa | grep -i xml'Affected if PyXML (pyxml) or the xml module is present and being used for parsing XML
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Identify the Python version in useRun 'python --version' or 'python3 --version' to get the Python interpreter versionAffected if Using Python 2.x (pre-3.3) which has weaker built-in hash randomization protections
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Check PYTHONHASHSEED environment variableRun 'echo $PYTHONHASHSEED' to see if hash randomization is enabled. A value of '0' disables randomization, while unset or a random numeric value enables itAffected if PYTHONHASHSEED is unset or set to 0, meaning hash tables are vulnerable to predictable collision attacks
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Verify if untrusted XML input is processedInspect application code for xml parsers (xml.dom.minidom, xml.etree, xml.sax) processing external or user-submitted XML documents. Search for parser instantiation patterns in application logs or configAffected if Applications parse untrusted or externally-sourced XML documents using PyXML's xml module
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Check Red Hat Enterprise Linux versionRun 'cat /etc/redhat-release' to identify the RHEL versionAffected if Running RHEL 5.0 or 6.0 which bundle the vulnerable PyXML library
You are affected if PyXML or the xml module is installed and your environment processes untrusted XML input without hash randomization (PYTHONHASHSEED unset or 0) on vulnerable Python/RHEL versions.
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 PyXML to a patched version, implement hash randomization via PYTHONHASHSEED, or migrate to a maintained XML library like lxml that includes protections against hash collision attacks.
Fix this in Pyxml
Scoped from the published advisory
- Consultation3.0 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 $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2012-0877 — 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-2012-0877 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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