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CVE-2019-20907: In Lib/tarfile.py in Python through 3.8.3, an attacker is able to craft a TAR archive leading to an infinit...

In Lib/tarfile.py in Python through 3.8.3, an attacker is able to craft a TAR archive leading to an infinite loop when opened by tarfile.open, because _proc_pax lacks header validation.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2019-20907 can make affected Python programs hang when they open a specially crafted TAR archive. The main business risk is service disruption in systems that accept or process TAR files from users, partners, build jobs, or automated feeds.

Executive priority

Treat as a targeted availability risk. Prioritize internet-facing upload services, automation pipelines, and business processes where a hung worker could block customer operations or build/deployment flow.

Technical view

Python's Lib/tarfile.py through 3.8.3 lacks validation in _proc_pax. A malformed PAX header can cause tarfile.open to enter an infinite loop, creating a denial-of-service condition for applications that parse untrusted TAR archives.

Likely exposure

Exposure is most likely in Python applications or automation that call tarfile.open on TAR archives from untrusted or semi-trusted sources. Systems using vendor-packaged Python should map installed versions to the relevant distro advisory.

Exploitation context

The source bundle does not report active exploitation, and KEV is false. Exploitation requires getting a crafted TAR archive processed by affected Python tarfile code; impact is described as an infinite loop rather than code execution.

Researcher notes

The bundle provides the root cause and advisory links but no CVSS, CWE, or precise package matrix. Validate exposure by runtime version, distro package status, and whether TAR parsing accepts attacker-influenced input.

Mitigation direction

  • Apply Python security updates from the relevant OS or Python vendor advisory.
  • Avoid processing untrusted TAR archives until affected runtimes are updated.
  • Add archive size, time, and worker isolation controls around TAR processing.
  • Check vendor guidance before assuming a specific package version is fixed.

Validation and detection

  • Inventory Python runtimes and packages on systems that process TAR files.
  • Search application code for tarfile.open handling user, partner, or pipeline-supplied archives.
  • Confirm installed packages match fixed versions in distro advisories.
  • Review upload, import, backup, and CI workflows for TAR ingestion paths.
Prepared
Confidence
medium
Sources
8

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

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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
24Source 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/an/an/aListed
Weakness

CWE details

No CWE listed

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