CVE-2019-25634: Base64 Decoder 1.1.2 contains a stack-based buffer overflow vulnerability that allows local attackers to execu

Routine

HIGH 8.4DOWNGRADE

CVE-2019-25634 is a high-severity flaw (CVSS 8.4) affecting base64 decoder. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.4 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 81%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-03-24
Last modified	2026-06-17

Publisher (CNA): VulnCheck · Vendor: 4mhz

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-24 12:16 UTCPublished CVE record published
2026-06-17 02:32 UTCUpdated Record last modified

4mhz base64 decoder DOWNGRADE

Affected: 1.1.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.1.2

1. Check installed version

apt-cache policy base64-decoder || rpm -q base64-decoder || base64-decoder --version

2. No fixed release: DOWNGRADE to a release before 1.1.2 (Debian / Ubuntu)

apt-cache madison base64-decoder sudo apt install base64-decoder=<VERSION_BEFORE_1.1.2> sudo apt-mark hold base64-decoder

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list base64-decoder sudo dnf downgrade base64-decoder-<VERSION_BEFORE_1.1.2> sudo dnf versionlock add base64-decoder

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2019-25634?

base64 decoder: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-25634 being exploited?

CVE-2019-25634 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2019-25634 affect?

CVE-2019-25634 affects base64 decoder. Severity is high (CVSS 8.4). 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 ov

How urgent is CVE-2019-25634?

Priority 39/100. High severity; Public exploit reference

References

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