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CVE Record

CVE-2021-3516: There's a flaw in libxml2's xmllint in versions before 2.9.11.

There's a flaw in libxml2's xmllint in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by xmllint could trigger a use-after-free. The greatest impact of this flaw is to confidentiality, integrity, and availability.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-3516 is a libxml2 xmllint flaw where a crafted file can trigger a use-after-free. Business risk depends on whether systems process untrusted XML or similar files with xmllint or affected libxml2 builds. The sources do not show active exploitation or a CVSS score.

Executive priority

Handle as a targeted dependency remediation item, not an emergency internet-wide incident based on available evidence. Prioritize environments that process untrusted files and vendor appliances listing libxml2 exposure.

Technical view

The issue is classified as CWE-416 use-after-free in libxml2's xmllint before 2.9.11. A crafted file submitted for processing may affect confidentiality, integrity, and availability. Public references include distribution advisories and an upstream GNOME libxml2 issue and commit, but the bundle does not provide exploit details.

Likely exposure

Exposure is most likely on servers, build pipelines, validation tools, or appliances that run xmllint or affected libxml2 packages against files supplied by users, partners, or automated feeds. Direct internet exposure is not established by the sources.

Exploitation context

The bundle states an attacker must be able to submit a crafted file for xmllint processing. CISA KEV status is false, and no cited source in the bundle confirms active exploitation. Treat exploitability evidence as incomplete.

Researcher notes

Key uncertainties are severity scoring, complete affected version mapping, and exploit availability. Distribution advisories and the upstream GNOME issue or commit are the best source-grounded starting points for patch lineage and backport verification.

Mitigation direction

  • Update libxml2 using the relevant OS or vendor security advisory.
  • Move to a vendor-fixed build for versions before 2.9.11.
  • Reduce or disable xmllint processing of untrusted files until patched.
  • Prioritize systems that parse externally supplied files automatically.
  • Check appliance vendor advisories where libxml2 is embedded.

Validation and detection

  • Inventory installed libxml2 packages and xmllint binaries.
  • Confirm package versions or vendor backport status against advisories.
  • Identify workflows that pass untrusted files to xmllint.
  • Review scanner results for CVE-2021-3516 on servers and appliances.
  • Document systems where libxml2 is embedded by third-party products.
Prepared
Confidence
medium
Sources
11

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-416: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2021-3516 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
10Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/alibxml2libxml2 2.9.11Listed
Weakness

CWE details

CWE-416

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

CWE-416 · source CWE mapping

Use After Free

Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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