CVE-2017-20228Public exploit

Local code execution via oversized source-file argument

Published Mar 28, 2026 · Updated Mar 28, 2026

Stack-based buffer overflow in Flat Assembler 1.71.21 allows local users to execute arbitrary code via an oversized source-file argument. The fasm command-line entry point accepts more than 5,895 bytes without adequate bounds checking, so the argument overwrites the saved instruction pointer. A local user who can invoke the 32-bit Linux build can run commands in the assembler process context; an unsuccessful attempt crashes that process.

CVSS severity8.6
High
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in Flat Assembler 1.71.21 allows local users to execute arbitrary code via an oversized source-file argument. The fasm command-line entry point accepts more than 5,895 bytes without adequate bounds checking, so the argument overwrites the saved instruction pointer. A local user who can invoke the 32-bit Linux build can run commands in the assembler process context; an unsuccessful attempt crashes that process.

The record

CVE
CVE-2017-20228
Published
Mar 28, 2026
Updated
Mar 28, 2026
Vendor
Tomasz Grysztar
Product
Flat Assembler
Classifications
CWE-787, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=1.71.21

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Tomasz Grysztar · Flat Assemblerversion=1.71.21

Published CVSS scores

8.6VulnCheckCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
8.4VulnCheckCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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