CVE-2006-5873: Buffer overflow in the cluster_process_heartbeat function in cluster.c in layer 2 tunneling protocol network s

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HIGH 7.8WATCHLISTDOWNGRADEMITIGATE

CVE-2006-5873 is a high-severity flaw (CVSS 7.8) affecting l2tpns, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in the cluster_process_heartbeat function in cluster.c in layer 2 tunneling protocol network server (l2tpns) before 2.1.21 allows remote attackers to cause a denial of service via a large heartbeat packet.

Why this priority

High severity
On your watchlist

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

Risk facts

CVSS score	7.8 (High)
EPSS exploit chance	2.3% (top 17%)
CISA exploited list	No
Published	2006-12-12
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: debian · l2tpns

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

Am I affected?

Timeline

2006-12-12 00:28 UTCPublished CVE record published
2026-06-16 22:32 UTCUpdated Record last modified

l2tpns l2tpns DOWNGRADE

Affected: 1.1 · 2.0.13 · 2.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.1

1. Check installed version

apt-cache policy l2tpns || rpm -q l2tpns || l2tpns --version

2. No fixed release: DOWNGRADE to a release before 1.1 (Debian / Ubuntu)

apt-cache madison l2tpns sudo apt install l2tpns=<VERSION_BEFORE_1.1> sudo apt-mark hold l2tpns

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

dnf --showduplicates list l2tpns sudo dnf downgrade l2tpns-<VERSION_BEFORE_1.1> sudo dnf versionlock add l2tpns

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.

debian debian linux MITIGATE

Affected: 3.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.1

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2006-5873?

l2tpns: downgrade or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2006-5873 being exploited?

CVE-2006-5873 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-2006-5873 affect?

CVE-2006-5873 affects l2tpns, debian linux. Severity is high (CVSS 7.8). Buffer overflow in the cluster_process_heartbeat function in cluster.c in layer 2 tunneling protocol network server (l2tpns) before 2.1.21 allows remote attackers to cause a denial of service via a large heartbeat packet.

How urgent is CVE-2006-5873?

Priority 53/100. High severity; On your watchlist

Software pages

Debian vulnerabilities

References

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