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CVE-2021-31566: An improper link resolution flaw can occur while extracting an archive leading to changing modes, times, ac...

An improper link resolution flaw can occur while extracting an archive leading to changing modes, times, access control lists, and flags of a file outside of the archive. An attacker may provide a malicious archive to a victim user, who would trigger this flaw when trying to extract the archive. A local attacker may use this flaw to gain more privileges in a system.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-31566 affects libarchive archive extraction. A malicious archive can cause metadata changes to files outside the archive, such as modes, timestamps, ACLs, or flags. The source bundle says a local attacker may use this to gain more privileges after a victim extracts the archive.

Executive priority

Treat as a practical hardening priority, not an emergency based on available evidence. Prioritize internet-facing or user-upload archive processing, build systems, and administrative workflows that extract files with high privileges.

Technical view

The flaw is CWE-59 improper link resolution during archive extraction. The issue is fixed in libarchive 3.5.2. The bundle does not provide CVSS scoring. Vendor advisories from Red Hat and Debian are referenced, indicating downstream package handling may vary by distribution.

Likely exposure

Exposure is most likely on systems or applications using libarchive without the 3.5.2 fix or a vendor backport, especially where untrusted archives are extracted by users or automated services.

Exploitation context

The bundle does not cite active exploitation, and KEV is false. Exploitation requires a malicious archive and extraction by a victim context. Impact depends on which files can be affected and whether extraction occurs with elevated privileges.

Researcher notes

Key uncertainty is affected version range beyond the stated fix in 3.5.2. Validate against vendor package metadata rather than upstream version alone because distributions may backport security fixes without changing major version numbers.

Mitigation direction

  • Upgrade libarchive to 3.5.2 or a vendor package containing the fix.
  • Check Red Hat, Debian, and other vendor guidance for backported package status.
  • Avoid extracting untrusted archives with elevated privileges.
  • Isolate archive extraction workflows that process user-supplied files.

Validation and detection

  • Inventory systems and applications that include or link libarchive.
  • Confirm installed packages include the CVE-2021-31566 fix or vendor backport.
  • Review workflows that extract untrusted or user-provided archives.
  • Verify privileged services do not extract attacker-controlled archives directly.
Prepared
Confidence
medium
Sources
6

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-59: 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-2021-31566 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
6Source 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/alibarchiveFixed in libarchive 3.5.2Listed
Weakness

CWE details

CWE-59

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

CWE-59 · source CWE mapping

Improper Link Resolution Before File Access ('Link Following')

Improper Link Resolution Before File Access ('Link Following') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs