#VU26104 NULL pointer dereference in ProFTPD - CVE-2019-19269

Vulnerability identifier: #VU26104

Vulnerability risk: Medium

CVSSv4.0: 4.6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2019-19269

CWE-ID: CWE-476

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
ProFTPD
Server applications / File servers (FTP/HTTP)

Vendor: ProFTPD

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference in tls_verify_crl() function in ProFTPD while processing data, returned by the OpenSSL sk_X509_REVOKED_value() function when encountering an empty CRL installed by a system administrator. A remote attacker can trigger the NULL pointer dereference error when validating the certificate of a client connecting to the server in a TLS client/server mutual-authentication setup.

Successful exploitation of the vulnerability will result in a denial of service condition.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

ProFTPD: 1.3.0a - 1.3.6

---

External links
https://lists.opensuse.org/opensuse-security-announce/2020-01/msg00009.html
https://github.com/proftpd/proftpd/issues/861
https://lists.debian.org/debian-lts-announce/2019/11/msg00039.html
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OGBBCPLJSDPFG5EI5P5G7P4KEX7YSD5G/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QR65XUHPCRU3NXTSFVF2J4GWRIHC7AHW/

---

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.