CVE-2019-25634
CVE-2019-25634 is a high-severity vulnerability in 4mhz Base64 Decoder with a CVSS 3.x base score of 8.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.
Key facts
- Severity: High (CVSS 3.x base score 8.4)
- CVSS v4: 8.6
- EPSS exploit prediction: 0% (18th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2019-20008
- Weakness: CWE-787
- Affected product: 4mhz Base64 Decoder
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2019-25634?
- 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.
- How severe is CVE-2019-25634?
- CVE-2019-25634 has a CVSS 3.x base score of 8.4, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2019-25634 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2019-25634?
- CVE-2019-25634 affects 4mhz Base64 Decoder. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2019-25634?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2019-25634 have an EU (EUVD) identifier?
- Yes. CVE-2019-25634 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2019-20008.
- When was CVE-2019-25634 published?
- CVE-2019-25634 was published on 2026-03-24 and last updated on 2026-06-17.
References
- http://4mhz.de/b64dec.html
- http://4mhz.de/download.php?file=b64dec-1-1-2.zip
- https://www.exploit-db.com/exploits/46625
- https://www.vulncheck.com/advisories/base64-decoder-local-buffer-overflow-seh-egghunter
Affected products (1)
- cpe:2.3:a:4mhz:base64_decoder:1.1.2:*:*:*:*:*:*:*
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