CVE-2011-5166: Multiple stack-based buffer overflows in KnFTP 1.0.0 allow remote attackers to execute arbitrary code via a lo

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HIGH 7.5DOWNGRADE

CVE-2011-5166 is a high-severity flaw (CVSS 7.5) affecting knftp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Multiple stack-based buffer overflows in KnFTP 1.0.0 allow remote attackers to execute arbitrary code via a long string to the (1) USER, (2) PASS, (3) REIN, (4) QUIT, (5) PORT, (6) PASV, (7) TYPE, (8) STRU, (9) MODE, (10) RETR, (11) STOR, (12) APPE, (13) ALLO, (14) REST, (15) RNFR, (16) RNTO, (17) ABOR, (18) DELE, (19) CWD, (20) LIST, (21) NLST, (22) SITE, (23) STST, (24) HELP, (25) NOOP, (26) MKD, (27) RMD, (28) PWD, (29) CDUP, (30) STOU, (31) S

Why this priority

High severity
EPSS top 6%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	6.5% (top 6%)
CISA exploited list	No
Weakness	CWE-119
Published	2012-09-15
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: elif keir

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

Am I affected?

Timeline

2012-09-15 17:55 UTCPublished CVE record published
2026-06-16 23:36 UTCUpdated Record last modified

elif keir knftp DOWNGRADE

Affected: 1.0.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.0.0 (Debian / Ubuntu)

apt-cache madison knftp sudo apt install knftp=<VERSION_BEFORE_1.0.0> sudo apt-mark hold knftp

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

dnf --showduplicates list knftp sudo dnf downgrade knftp-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add knftp

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.

Public exploits and detection

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

Exploit-DB: KnFTP 1.0.0 Server - Multiple Buffer Overflows (PoC) (SEH)
Exploit-DB: KnFTP 1.0 - Remote Buffer Overflow (DEP Bypass) (Metasploit)
Exploit-DB: KnFTP 1.0.0 Server - 'USER' Remote Buffer Overflow
Exploit-DB: KnFTP Server - Remote 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-2011-5166?

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

Is CVE-2011-5166 being exploited?

CVE-2011-5166 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-2011-5166 affect?

CVE-2011-5166 affects knftp. Severity is high (CVSS 7.5). Multiple stack-based buffer overflows in KnFTP 1.0.0 allow remote attackers to execute arbitrary code via a long string to the (1) USER, (2) PASS, (3) REIN, (4) QUIT, (5) PORT, (6) PASV, (7) TYPE, (8) STRU, (9) MODE, (10) RETR, (11) STOR, (

How urgent is CVE-2011-5166?

Priority 55/100. High severity; EPSS top 6%: very likely to be exploited; Public exploit reference

References

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