CVE-2001-0534: Multiple buffer overflows in RADIUS daemon radiusd in (1) Merit 3.6b and (2) Lucent 2.1-2 RADIUS allow remote

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HIGH 10.0DOWNGRADEDOWNGRADE

CVE-2001-0534 is a high-severity flaw (CVSS 10.0) affecting radius, radius. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Multiple buffer overflows in RADIUS daemon radiusd in (1) Merit 3.6b and (2) Lucent 2.1-2 RADIUS allow remote attackers to cause a denial of service or execute arbitrary commands.

Why this priority

Critical severity
EPSS top 6%: very likely to be exploited

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

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	6.7% (top 6%)
CISA exploited list	No
Published	2001-07-21
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: lucent · merit

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2001-07-21 04:00 UTCPublished CVE record published
2026-06-16 21:54 UTCUpdated Record last modified

lucent radius DOWNGRADE

Affected: 2.1.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.1.2

1. Check installed version

apt-cache policy radius || rpm -q radius || radius --version

2. No fixed release: DOWNGRADE to a release before 2.1.2 (Debian / Ubuntu)

apt-cache madison radius sudo apt install radius=<VERSION_BEFORE_2.1.2> sudo apt-mark hold radius

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

dnf --showduplicates list radius sudo dnf downgrade radius-<VERSION_BEFORE_2.1.2> sudo dnf versionlock add radius

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.

merit radius DOWNGRADE

Affected: 3.6b

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.6b

1. Check installed version

apt-cache policy radius || rpm -q radius || radius --version

2. No fixed release: DOWNGRADE to a release before 3.6b (Debian / Ubuntu)

apt-cache madison radius sudo apt install radius=<VERSION_BEFORE_3.6b> sudo apt-mark hold radius

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

dnf --showduplicates list radius sudo dnf downgrade radius-<VERSION_BEFORE_3.6b> sudo dnf versionlock add radius

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-2001-0534?

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

Is CVE-2001-0534 being exploited?

CVE-2001-0534 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-2001-0534 affect?

CVE-2001-0534 affects radius, radius. Severity is high (CVSS 10.0). Multiple buffer overflows in RADIUS daemon radiusd in (1) Merit 3.6b and (2) Lucent 2.1-2 RADIUS allow remote attackers to cause a denial of service or execute arbitrary commands.

How urgent is CVE-2001-0534?

Priority 58/100. Critical severity; EPSS top 6%: very likely to be exploited

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References

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