Security Bulletin: IBM Flex System switch firmware products are affected by TCP denial of service vulnerabilities

Summary

IBM Flex System switch firmware products have addressed the following TCP denial of service vulnerabilities.

Vulnerability Details

CVEID:CVE-2019-11478
**DESCRIPTION:**Jonathan Looney discovered that the TCP retransmission queue implementation in tcp_fragment in the Linux kernel could be fragmented when handling certain TCP Selective Acknowledgment (SACK) sequences. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commit f070ef2ac66716357066b683fb0baf55f8191a2e.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/162664 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

CVEID:CVE-2019-11477
**DESCRIPTION:**Jonathan Looney discovered that the TCP_SKB_CB(skb)->tcp_gso_segs value was subject to an integer overflow in the Linux kernel when handling TCP Selective Acknowledgments (SACKs). A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commit 3b4929f65b0d8249f19a50245cd88ed1a2f78cff.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/162662 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

CVEID:CVE-2019-11479
**DESCRIPTION:**Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes. This allows a remote peer to fragment TCP resend queues significantly more than if a larger MSS were enforced. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commits 967c05aee439e6e5d7d805e195b3a20ef5c433d6 and 5f3e2bf008c2221478101ee72f5cb4654b9fc363.
CVSS Base score: 7.5
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/162665 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Affected Products and Versions

Product

|

Affected Version

—|—
IBM Flex System Fabric EN4093/EN4093R 10Gb Scalable Switch firmware |

7.8

IBM Flex System EN2092 1Gb Ethernet Scalable firmware

|

7.8

IBM Flex System Fabric SI4093 System Interconnect Module firmware

|

7.8

IBM Flex System Fabric CN4093 10Gb ScSE firmware

|

7.8

Remediation/Fixes

Firmware fix versions are available on Fix Central: <http://www.ibm.com/support/fixcentral/&gt;

Product

|

Fix Version

—|—
IBM Flex System Fabric EN4093/EN4093R 10Gb Scalable Switch firmware
(ibm_fw_scsw_en4093r-7.8.24.0_anyos_noarch)

|

7.8.24.0

IBM Flex System EN2092 1Gb Ethernet Scalable firmware
(ibm_fw_scsw_en2092-7.8.24.0_anyos_noarch)

|

7.8.24.0

IBM Flex System Fabric SI4093 System Interconnect Module firmware
(ibm_fw_scsw_si4093-7.8.24.0_anyos_noarch)

|

7.8.24.0

IBM Flex System Fabric CN4093 10Gb ScSE firmware
(ibm_fw_scsw_cn4093-7.8.24.0_anyos_noarch)

|

7.8.24.0

Workarounds and Mitigations

Firmware fix versions are available on Fix Central: <http://www.ibm.com/support/fixcentral/&gt;

Product

|

Fix Version

—|—
IBM Flex System Fabric EN4093/EN4093R 10Gb Scalable Switch firmware
(ibm_fw_scsw_en4093r-7.8.24.0_anyos_noarch)

|

7.8.24.0

IBM Flex System EN2092 1Gb Ethernet Scalable firmware
(ibm_fw_scsw_en2092-7.8.24.0_anyos_noarch)

|

7.8.24.0

IBM Flex System Fabric SI4093 System Interconnect Module firmware
(ibm_fw_scsw_si4093-7.8.24.0_anyos_noarch)

|

7.8.24.0

IBM Flex System Fabric CN4093 10Gb ScSE firmware
(ibm_fw_scsw_cn4093-7.8.24.0_anyos_noarch)

|

7.8.24.0