CVE-2019-25634Public exploit

Local code execution via SEH chain overwrite

Published Mar 24, 2026 · Updated Mar 24, 2026

Stack-based buffer overflow in 4Mhz Base64 Decoder 1.1.2 allows local users to execute arbitrary code via a crafted input file. Processing the oversized file writes beyond a stack buffer and replaces the SEH chain with a POP-POP-RET address that redirects execution to an egghunter payload. The file must be processed locally; successful exploitation runs shellcode with the application's privileges on Windows.

CVSS severity8.6
High
EPSS probability0.26%
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 4Mhz Base64 Decoder 1.1.2 allows local users to execute arbitrary code via a crafted input file. Processing the oversized file writes beyond a stack buffer and replaces the SEH chain with a POP-POP-RET address that redirects execution to an egghunter payload. The file must be processed locally; successful exploitation runs shellcode with the application's privileges on Windows.

The record

CVE
CVE-2019-25634
Published
Mar 24, 2026
Updated
Mar 24, 2026
Vendor
4Mhz
Product
Base64 Decoder
Classifications
CWE-787, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.1.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

4Mhz · Base64 Decoderversion=1.1.2

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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