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Vulnerability record · CVE-2019-25634 · published 24 March 2026

CVE-2019-25634: 4mhz base64 decoder out-of-bounds write vulnerability

44mhz · Base64 Decoder

Base64 Decoder 1.1.2 contains a stack-based buffer overflow vulnerability that allows local attackers to execute arbitrary code by triggering a structured exception handler (SEH) overwrite. Attackers can craft a malicious input file that overflows a buffer, overwrites the SEH chain with a POP-POP-RET gadget address, and uses an egghunter payload to locate and execute shellcode for code execution.

8.6 CVSS 4.0 High EPSS 0.26% · top 83.8% CWE-787 · Out-of-bounds write
8.6CVSS 4.0 base score
0.26%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 1 tagged exploit
17 Jun 2026Last modified by NVD

Description

Base64 Decoder 1.1.2 contains a stack-based buffer overflow vulnerability that allows local attackers to execute arbitrary code by triggering a structured exception handler (SEH) overwrite. Attackers can craft a malicious input file that overflows a buffer, overwrites the SEH chain with a POP-POP-RET gadget address, and uses an egghunter payload to locate and execute shellcode for code execution.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://4mhz.de/b64dec.html ProductRelease Notes
http://4mhz.de/download.php?file=b64dec-1-1-2.zip Product
https://www.exploit-db.com/exploits/46625 Exploit
https://www.vulncheck.com/advisories/base64-decoder-local-buffer-overflow-seh-egghunter Third Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2019-25634), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.