CVE-1999-1539: Buffer overflow in FTP server in QPC Software's QVT/Term Plus versions 4.2d and 4.3 and QVT/Net 4.3 allows rem

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HIGH 7.5DOWNGRADEDOWNGRADE

CVE-1999-1539 is a high-severity flaw (CVSS 7.5) affecting qvt net, qvt term plus. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in FTP server in QPC Software's QVT/Term Plus versions 4.2d and 4.3 and QVT/Net 4.3 allows remote attackers to cause a denial of service, and possibly execute arbitrary commands, via a long (1) user name or (2) password.

Why this priority

High severity
EPSS top 4%: 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	12.1% (top 4%)
CISA exploited list	No
Published	1999-11-10
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: qpc software

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

Am I affected?

Timeline

1999-11-10 05:00 UTCPublished CVE record published
2026-06-16 21:50 UTCUpdated Record last modified

qpc software qvt net DOWNGRADE

Affected: 4.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.3

1. Check installed version

apt-cache policy qvt-net || rpm -q qvt-net || qvt-net --version

2. No fixed release: DOWNGRADE to a release before 4.3 (Debian / Ubuntu)

apt-cache madison qvt-net sudo apt install qvt-net=<VERSION_BEFORE_4.3> sudo apt-mark hold qvt-net

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

dnf --showduplicates list qvt-net sudo dnf downgrade qvt-net-<VERSION_BEFORE_4.3> sudo dnf versionlock add qvt-net

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.

qpc software qvt term plus DOWNGRADE

Affected: 4.2d · 4.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.2d

1. Check installed version

apt-cache policy qvt-term-plus || rpm -q qvt-term-plus || qvt-term-plus --version

2. No fixed release: DOWNGRADE to a release before 4.2d (Debian / Ubuntu)

apt-cache madison qvt-term-plus sudo apt install qvt-term-plus=<VERSION_BEFORE_4.2d> sudo apt-mark hold qvt-term-plus

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

dnf --showduplicates list qvt-term-plus sudo dnf downgrade qvt-term-plus-<VERSION_BEFORE_4.2d> sudo dnf versionlock add qvt-term-plus

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: QPC Software QVT Term 4.3/QVT/Net 4.3 Suite FTP Server - Denial of Service

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-1999-1539?

qvt net: downgrade or apply the listed mitigation; qvt term plus: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-1999-1539 being exploited?

CVE-1999-1539 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-1999-1539 affect?

CVE-1999-1539 affects qvt net, qvt term plus. Severity is high (CVSS 7.5). Buffer overflow in FTP server in QPC Software's QVT/Term Plus versions 4.2d and 4.3 and QVT/Net 4.3 allows remote attackers to cause a denial of service, and possibly execute arbitrary commands, via a long (1) user name or (2) password.

How urgent is CVE-1999-1539?

Priority 55/100. High severity; EPSS top 4%: very likely to be exploited; Public exploit reference

Related CVEs

CVE-2001-0681 MEDIUM 5.0 DOWNGRADE DOWNGRADE Buffer overflow in ftpd in QPC QVT/Net 5.0 and QVT/Term 5.0 allows a remote attacker to cause a denial of serv
CVE-2001-0680 MEDIUM 5.0 DOWNGRADE DOWNGRADE Directory traversal vulnerability in ftpd in QPC QVT/Net 4.0 and AVT/Term 5.0 allows a remote attacker to trav
CVE-2001-0443 HIGH 7.5 DOWNGRADE DOWNGRADE Buffer overflow in QPC QVT/Net Popd 4.20 in QVT/Net 5.0 allows remote attackers to cause a denial of service,

References

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