CVE-2019-25686: Core FTP 2.0 build 653 contains a denial of service vulnerability in the PBSZ command that allows unauthentica

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HIGH 7.5REMOTEDOWNGRADE

CVE-2019-25686 is a high-severity flaw (CVSS 7.5) affecting core ftp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Core FTP 2.0 build 653 contains a denial of service vulnerability in the PBSZ command that allows unauthenticated attackers to crash the service by sending a malformed command with an oversized buffer. Attackers can send a PBSZ command with a payload exceeding 211 bytes to trigger an access violation and crash the FTP server process.

Why this priority

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

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

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 60%)
CISA exploited list	No
Weakness	CWE-306
Published	2026-04-05
Last modified	2026-07-24

Publisher (CNA): VulnCheck · Vendor: coreftp

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-05 21:16 UTCPublished CVE record published
2026-07-24 22:10 UTCUpdated Record last modified

coreftp core ftp DOWNGRADE

Affected: 2.0 build_653

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0

1. Check installed version

apt-cache policy core-ftp || rpm -q core-ftp || core-ftp --version

2. No fixed release: DOWNGRADE to a release before 2.0 (Debian / Ubuntu)

apt-cache madison core-ftp sudo apt install core-ftp=<VERSION_BEFORE_2.0> sudo apt-mark hold core-ftp

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

dnf --showduplicates list core-ftp sudo dnf downgrade core-ftp-<VERSION_BEFORE_2.0> sudo dnf versionlock add core-ftp

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.

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-2019-25686?

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

Is CVE-2019-25686 being exploited?

CVE-2019-25686 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-2019-25686 affect?

CVE-2019-25686 affects core ftp. Severity is high (CVSS 7.5). Core FTP 2.0 build 653 contains a denial of service vulnerability in the PBSZ command that allows unauthenticated attackers to crash the service by sending a malformed command with an oversized buffer. Attackers can send a PBSZ command with

How urgent is CVE-2019-25686?

Priority 46/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2019-25654 HIGH 7.5 DOWNGRADE Core FTP/SFTP Server 1.2 contains a buffer overflow vulnerability that allows attackers to crash the service b

References

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