CVE-2020-11909: The Treck TCP/IP stack before 6.0.1.66 has an IPv4 Integer Underflow.

Q: How do I fix CVE-2020-11909?

tcp\/ip: upgrade to 6.0.1.66. Exact commands for each OS are on this page.

Q: Is CVE-2020-11909 being exploited?

CVE-2020-11909 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-2020-11909 affect?

CVE-2020-11909 affects tcp\/ip. Severity is medium (CVSS 5.3). The Treck TCP/IP stack before 6.0.1.66 has an IPv4 Integer Underflow.

Q: How urgent is CVE-2020-11909?

Priority 51/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2020-11909 is a medium-severity flaw (CVSS 5.3) affecting tcp\/ip. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Treck TCP/IP stack before 6.0.1.66 has an IPv4 Integer Underflow.

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.6% (top 11%)
CISA exploited list	No
Weakness	CWE-191
Published	2020-06-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: treck

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

Am I affected?

Timeline

2020-06-17 11:15 UTCPublished CVE record published
2026-06-17 02:51 UTCUpdated Record last modified

treck tcp\/ip UPGRADE

Affected: < 6.0.1.66

Fixed in: 6.0.1.66

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 6.0.1.66 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tcpip

Note

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

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-2020-11909?

tcp\/ip: upgrade to 6.0.1.66. Exact commands for each OS are on this page.

Is CVE-2020-11909 being exploited?

CVE-2020-11909 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-2020-11909 affect?

CVE-2020-11909 affects tcp\/ip. Severity is medium (CVSS 5.3). The Treck TCP/IP stack before 6.0.1.66 has an IPv4 Integer Underflow.

How urgent is CVE-2020-11909?

Priority 51/100. Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-25066 CRITICAL 10.0 UPGRADE A heap-based buffer overflow in the Treck HTTP Server component before 6.0.1.68 allows remote attackers to cau
CVE-2020-11914 MEDIUM 4.3 UPGRADE The Treck TCP/IP stack before 6.0.1.66 has an ARP Out-of-bounds Read.
CVE-2020-11913 MEDIUM 5.3 UPGRADE The Treck TCP/IP stack before 6.0.1.66 has an IPv6 Out-of-bounds Read.
CVE-2020-11912 MEDIUM 5.3 UPGRADE The Treck TCP/IP stack before 6.0.1.66 has a TCP Out-of-bounds Read.
CVE-2020-11911 MEDIUM 5.3 UPGRADE The Treck TCP/IP stack before 6.0.1.66 has Improper ICMPv4 Access Control.

References

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