CVE-2017-20228

HIGH

Flat Assembler 1.71.21 Stack-Based Buffer Overflow ROP

Title source: cna
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2017-20228. PoCs published by Juan Sacco.

AI-analyzed exploit summary This exploit demonstrates a stack-based buffer overflow in FASM 1.7.21, leveraging ROP (Return-Oriented Programming) to bypass NX and execute arbitrary code (specifically, spawning a shell). The exploit constructs a ROP chain to write '/bin//sh' into memory and invoke execve.

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.

Exploits (1)

exploitdb WORKING POC
by Juan Sacco · pythonlocallinux
https://www.exploit-db.com/exploits/42265

This exploit demonstrates a stack-based buffer overflow in FASM 1.7.21, leveraging ROP (Return-Oriented Programming) to bypass NX and execute arbitrary code (specifically, spawning a shell). The exploit constructs a ROP chain to write '/bin//sh' into memory and invoke execve.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: FASM (Flat Assembler) 1.7.21 and prior
No auth needed
Prerequisites: FASM 1.7.21 or prior installed on a vulnerable system · Ability to execute the exploit script on the target system
devstral-2 · analyzed Apr 08, 2026 Full analysis →

References (3)

Core 3
Core References
Exploit exploit
ExploitDB-42265
https://www.exploit-db.com/exploits/42265
Product product
Official Product Homepage
http://www.flatassembler.net
Third Party Advisory third-party-advisory
VulnCheck Advisory: Flat Assembler 1.71.21 Stack-Based Buffer Overflow ROP
https://www.vulncheck.com/advisories/flat-assembler-stack-based-buffer-overflow-rop

Scores

CVSS v3 8.4
EPSS 0.0022
EPSS Percentile 12.3%
Attack Vector LOCAL
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact total

Details

CWE
CWE-787
Status published
Products (2)
Flatassembler/Flat Assembler 1.71.21
flatassembler/flat_assembler < 1.71.21
Published Mar 28, 2026
Tracked Since Mar 29, 2026