Vulnerability identifier: #VU23427

Vulnerability risk: Medium

CVSSv3.1: 6.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2019-8460

CWE-ID: CWE-400

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
OpenBSD
Operating systems & Components / Operating system

Vendor: OpenBSD

Description

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

The vulnerability exists due to an error when processing TCP SACK packets. A remote attacker can force the system to create long chains of TCP SACK holes that causes very expensive calls to tcp_sack_option() for every incoming SACK packet.

Successful exploitation of the vulnerability may result in a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

OpenBSD: 6.0 - 6.5

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External links
http://ftp.openbsd.org/pub/OpenBSD/patches/6.5/common/006_tcpsack.patch.sig
http://github.com/openbsd/src/commit/ed8fdce754a5d8d14c09e989d8877707bd43906f
http://research.checkpoint.com/tcp-sack-security-issue-in-openbsd-cve-2019-8460/

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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. However, proof of concept for this vulnerability is available.