OpenBSD kernel version <= 6.5 can be forced to create long chains of TCP SACK holes that causes very expensive calls to tcp_sack_option() for every incoming SACK packet which can lead to a denial of service.

Reuven Plevinsky and Tal Vainshtein of Check Point Software Technologies Ltd. discovered that OpenBSD kernel (all versions, including 6.5) can be forced to create long chains of TCP SACK holes that cause very expensive calls to tcp_sack_option() for every incoming SACK packet which can lead to a denial of service.

The kernel can be forced to make very expensive calls for every incoming TCP Selective Acknowledgement (SACK) packet which can lead to a denial-of-service condition. CVE-2019-8460 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). The kernel is affected by an integer overflow when handling TCP Selective Acknowledgements, which could allow a remote attacker to cause a denial-of-service condition. CVE-2019-11477 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). A remote attacker sending specially crafted TCP Selective Acknowledgment (SACK) sequences may cause a denial-of-service condition. CVE-2019-11478 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L). An attacker may exploit a vulnerability in the TCP retransmission queue implementation kernel when handling TCP Selective Acknowledgements (SACK) to cause a denial-of-service condition. CVE-2019-11479 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in OpenBSD ausnutzen, um einen Denial of Service Angriff durchzuführen.