CVE-2011-4862: Buffer overflow in libtelnet/encrypt.c in telnetd in FreeBSD 7.3 through 9.0, MIT Kerberos Version 5 Applicati

Q: How do I fix CVE-2011-4862?

inetutils: upgrade to 1.9; heimdal: upgrade to newer than 1.5.1; krb5-appl: upgrade to newer than 1.0.2. Exact commands for each OS are on this page.

Q: Is CVE-2011-4862 being exploited?

CVE-2011-4862 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2011-4862 affect?

CVE-2011-4862 affects inetutils, heimdal, krb5-appl. Severity is high (CVSS 10.0). Buffer overflow in libtelnet/encrypt.c in telnetd in FreeBSD 7.3 through 9.0, MIT Kerberos Version 5 Applications (aka krb5-appl) 1.0.2 and earlier, Heimdal 1.5.1 and earlier, GNU inetutils, and possibly other products allows remote attacke

Q: How urgent is CVE-2011-4862?

Priority 70/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference; On your watchlist

This week

HIGH 10.0WATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2011-4862 is a high-severity flaw (CVSS 10.0) affecting inetutils, heimdal, krb5-appl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in libtelnet/encrypt.c in telnetd in FreeBSD 7.3 through 9.0, MIT Kerberos Version 5 Applications (aka krb5-appl) 1.0.2 and earlier, Heimdal 1.5.1 and earlier, GNU inetutils, and possibly other products allows remote attackers to execute arbitrary code via a long encryption key, as exploited in the wild in December 2011.

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	95.1% (top 1%)
CISA exploited list	No
Weakness	CWE-120
Published	2011-12-25
Last modified	2026-06-16

Publisher (CNA): FreeBSD · Vendor: debian · fedoraproject · freebsd · gnu · heimdal project · mit

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

Am I affected?

Timeline

2011-12-25 01:55 UTCPublished CVE record published
2026-06-16 23:35 UTCUpdated Record last modified

gnu inetutils UPGRADE

Affected: < 1.9

Fixed in: 1.9

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade inetutils

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade inetutils

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

heimdal project heimdal UPGRADE

Affected: <= 1.5.1

Fixed in: newer than 1.5.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.5.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade heimdal

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade heimdal

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

mit krb5-appl UPGRADE

Affected: <= 1.0.2

Fixed in: newer than 1.0.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy krb5-appl || rpm -q krb5-appl || krb5-appl --version

2. UPGRADE to newer than 1.0.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade krb5-appl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade krb5-appl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

freebsd freebsd UPGRADE

Affected: >= 7.3 and <= 9.0

Fixed in: newer than 9.0

Safe to downgrade to: a release before 7.3

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.

fedoraproject fedora MITIGATE

Affected: 15 · 16

Fixed in: no fixed release known

Safe to downgrade to: a release before 15

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.

debian debian linux MITIGATE

Affected: 5.0 · 6.0 · 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 5.0

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · rust-tokio · FIXED · 1.54.1-1.fc46 · FEDORA-2026-e7fd815169 · source

sudo dnf upgrade --advisory=FEDORA-2026-e7fd815169

Fedora ELN · libopenraw · FIXED · 0.3.7-2.eln159 · FEDORA-2026-3fa115dd38 · source

sudo dnf upgrade --advisory=FEDORA-2026-3fa115dd38

Debian 12 · heimdal · FIXED · 1.5.dfsg.1-1

sudo apt update && sudo apt install --only-upgrade heimdal dpkg --compare-versions "$(dpkg-query -W -f='${Version}' heimdal)" ge "1.5.dfsg.1-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · heimdal · FIXED · 1.5.dfsg.1-1

sudo apt update && sudo apt install --only-upgrade heimdal dpkg --compare-versions "$(dpkg-query -W -f='${Version}' heimdal)" ge "1.5.dfsg.1-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · inetutils · FIXED · 2:1.8-6

sudo apt update && sudo apt install --only-upgrade inetutils dpkg --compare-versions "$(dpkg-query -W -f='${Version}' inetutils)" ge "2:1.8-6" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · inetutils · FIXED · 2:1.8-6

sudo apt update && sudo apt install --only-upgrade inetutils dpkg --compare-versions "$(dpkg-query -W -f='${Version}' inetutils)" ge "2:1.8-6" && echo PATCHED || echo STILL-VULNERABLE

RHEL 3 Extended Lifecycle Support · krb5 · FIXED · krb5-1.2.7-73

sudo dnf upgrade --advisory=RHSA-2011:1853 rpm -q krb5

RHEL 4 · krb5 · FIXED · krb5-1.3.4-65.el4

sudo dnf upgrade --advisory=RHSA-2011:1851 rpm -q krb5

RHEL 5 · krb5 · FIXED · krb5-1.6.1-63.el5_7

sudo dnf upgrade --advisory=RHSA-2011:1851 rpm -q krb5

RHEL 5.3 Long Life · krb5 · FIXED · krb5-1.6.1-31.el5_3.5

sudo dnf upgrade --advisory=RHSA-2011:1853 rpm -q krb5

RHEL 5.6 EUS - Server Only · krb5 · FIXED · krb5-1.6.1-55.el5_6.3

sudo dnf upgrade --advisory=RHSA-2011:1853 rpm -q krb5

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: hdbreaker/GO-CVE-2011-4862 (5 stars)
GitHub PoC: appsecrani/CVE-2011-4862 (1 stars)
Exploit-DB: FreeBSD - Telnet Service Encryption Key ID Buffer Overflow (Metasploit)
Exploit-DB: Linux BSD-derived Telnet Service Encryption Key ID - Remote Buffer Overflow (Metasploit)
Exploit-DB: TelnetD encrypt_keyid - Function Pointer Overwrite
Metasploit: Telnet Service Encryption Key ID Overflow Detection
Metasploit: FreeBSD Telnet Service Encryption Key ID Buffer Overflow
Metasploit: Linux BSD-derived Telnet Service Encryption Key ID Buffer Overflow

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-2011-4862?

inetutils: upgrade to 1.9; heimdal: upgrade to newer than 1.5.1; krb5-appl: upgrade to newer than 1.0.2. Exact commands for each OS are on this page.

Is CVE-2011-4862 being exploited?

CVE-2011-4862 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-2011-4862 affect?

CVE-2011-4862 affects inetutils, heimdal, krb5-appl. Severity is high (CVSS 10.0). Buffer overflow in libtelnet/encrypt.c in telnetd in FreeBSD 7.3 through 9.0, MIT Kerberos Version 5 Applications (aka krb5-appl) 1.0.2 and earlier, Heimdal 1.5.1 and earlier, GNU inetutils, and possibly other products allows remote attacke

How urgent is CVE-2011-4862?

Priority 70/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

Debian vulnerabilities

Related CVEs

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CVE-2026-32746 CRITICAL 9.8 UPGRADE telnetd in GNU inetutils through 2.7 allows an out-of-bounds write in the LINEMODE SLC (Set Local Characters)
CVE-2026-28372 HIGH 7.4 UPGRADE telnetd in GNU inetutils through 2.7 allows privilege escalation that can be exploited by abusing systemd serv
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References

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