Stack-Based Buffer Overflow in Base64 Decoder by 4MHz
CVE-2019-25634

8.6HIGH

Key Information:

Vendor

4mhz

Status
Base64 Decoder
Vendor
CVE Published:
24 March 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2019-25634?

The Base64 Decoder version 1.1.2 exhibits a stack-based buffer overflow vulnerability that can be exploited by local attackers. By crafting a malicious input file, an attacker can trigger an overwrite of the structured exception handler (SEH) chain. This leads to the possibility of executing arbitrary code through a carefully positioned POP-POP-RET gadget. The exploitation involves an egghunter payload that facilitates locating and executing shellcode, thereby jeopardizing the security and integrity of the affected system.

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Affected Version(s)

Base64 Decoder 1.1.2

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2019-25634 - Proof of Concept

References

https://www.exploit-db.com/exploits/46625
exploit
http://4mhz.de/b64dec.html
product
http://4mhz.de/download.php?file=b64dec-1-1-2.zip
product

CVSS V4

Score:
8.6
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Paolo Perego - paolo@armoredcode.com
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