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CVE Record

CVE-2021-33644: An attacker who submits a crafted tar file with size in header struct being 0 may be able to trigger an cal...

An attacker who submits a crafted tar file with size in header struct being 0 may be able to trigger an calling of malloc(0) for a variable gnu_longname, causing an out-of-bounds read.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-33644 affects libtar before 1.2.21. A malicious tar archive can cause the library to read outside expected memory while handling a malformed long-name header. Business risk is concentrated in systems that accept, unpack, scan, or transform tar files from users, partners, or automated feeds.

Executive priority

Treat as a targeted patching item, not an emergency, unless the organization processes untrusted tar files at scale or on internet-facing services.

Technical view

The reported flaw is CWE-125 in libtar. A crafted tar header with size set to 0 can lead to malloc(0) for gnu_longname and an out-of-bounds read. The supplied sources identify affected versions as libtar before 1.2.21 and include Fedora, openEuler, and Debian LTS advisories.

Likely exposure

Exposure is likely where libtar is installed directly or bundled into software that processes tar archives, especially upload pipelines, package handling, backup restore paths, and security scanning workflows.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation. Exploitation requires an attacker-controlled crafted tar file being processed by vulnerable libtar code.

Researcher notes

Evidence is limited to the CVE description and distribution advisories. No CVSS vector, exploit status, or detailed fix notes were provided in the bundle, so impact should be validated against local libtar usage and vendor package metadata.

Mitigation direction

  • Inventory systems and applications using libtar.
  • Upgrade libtar to 1.2.21 or vendor-fixed packages where available.
  • Prioritize internet-facing or user-upload archive processing paths.
  • Limit processing of untrusted tar files until vulnerable instances are patched.
  • Track Fedora, Debian LTS, openEuler, and upstream advisories for package guidance.

Validation and detection

  • Check installed libtar package versions against the <1.2.21 affected range.
  • Identify services that parse tar files from users, partners, or automation.
  • Confirm patched vendor package versions are deployed on affected Linux distributions.
  • Review archive-processing crash reports for unexplained failures, without assuming exploitation.
  • Run normal archive workflow regression tests after patching.
Prepared
Confidence
medium
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

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-125: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-33644 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
8Source 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/alibtar<1.2.21Listed
Weakness

CWE details

CWE-125

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