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CVE Record

CVE-2022-2309: NULL Pointer Dereference in lxml/lxml

NULL Pointer Dereference allows attackers to cause a denial of service (or application crash). This only applies when lxml is used together with libxml2 2.9.10 through 2.9.14. libxml2 2.9.9 and earlier are not affected. It allows triggering crashes through forged input data, given a vulnerable code sequence in the application. The vulnerability is caused by the iterwalk function (also used by the canonicalize function). Such code shouldn't be in wide-spread use, given that parsing + iterwalk would usually be replaced with the more efficient iterparse function. However, an XML converter that serialises to C14N would also be vulnerable, for example, and there are legitimate use cases for this code sequence. If untrusted input is received (also remotely) and processed via iterwalk function, a crash can be triggered.

MediumCVSS 5.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This CVE can let malformed XML crash an application that uses lxml in a specific way. The business impact is service interruption, not data theft or code execution, based on the provided sources. Exposure is narrower than simply using lxml because it depends on libxml2 versions and specific XML processing functions.

Executive priority

Treat as a targeted availability risk. Prioritize internet-facing or business-critical XML processors first, especially converters or services accepting user-supplied XML. It is not evidenced as actively exploited or confidentiality-impacting in the provided sources.

Technical view

CVE-2022-2309 is a NULL pointer dereference in lxml when used with libxml2 2.9.10 through 2.9.14. The crash is tied to iterwalk, also used by canonicalize, when forged input reaches a vulnerable application code sequence. CVSS is 5.3 with availability impact only.

Likely exposure

Most likely exposed systems are Python applications using lxml with libxml2 2.9.10-2.9.14 that process untrusted XML through iterwalk or canonicalize/C14N conversion paths. The source bundle does not provide a complete lxml version range.

Exploitation context

The source bundle says crashes can be triggered remotely when untrusted input reaches the vulnerable path. KEV is false, and the provided sources do not establish active exploitation in the wild.

Researcher notes

The important constraint is the application code path: lxml plus libxml2 2.9.10-2.9.14 is not enough without iterwalk/canonicalize exposure. Upstream has a referenced commit, but the bundle does not enumerate every fixed downstream package version.

Mitigation direction

  • Follow lxml, OS distribution, and vendor advisories for fixed package versions.
  • Update affected lxml/libxml2 packages where vendor fixes are available.
  • Avoid iterwalk or canonicalize on untrusted XML when a safer design is feasible.
  • Use iterparse where it fits the application’s XML processing needs.
  • Isolate or restart XML-processing services to reduce denial-of-service impact.

Validation and detection

  • Inventory applications importing lxml and their linked libxml2 versions.
  • Search code for iterwalk, canonicalize, and C14N XML conversion paths.
  • Identify whether those paths process remote or otherwise untrusted XML.
  • Compare installed packages against Gentoo, Fedora, Debian, NetApp, and upstream guidance.
  • Confirm remediation with non-offensive regression tests for XML handling and service stability.
Prepared
Confidence
high
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-476: Exact CWE lookup

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cve · low confidence lookup

CVE-2022-2309 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.3 (3.0)
Known Exploited
No
Published

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
8Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.3CVSS 3.0MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L3.91.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.0 score

5.3Medium
CVSS 3.0 vector shape for CVE-2022-2309Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
lxmllxml/lxmlunspecifiedListed
Weakness

CWE details

CWE-476

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-476 · source CWE mapping

NULL Pointer Dereference

NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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