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2021-07 Security Bulletin: Junos OS Evolved: Multiple kernel vulnerabilities resolved

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Article ID: JSA11205 SECURITY_ADVISORIES Last Updated: 14 Jul 2021Version: 1.0
Product Affected:
These issues affect Junos OS Evolved.
Problem:

Multiple vulnerabilities have been resolved in Juniper Networks Junos OS Evolved by upgrading the kernel.

These issues affect Juniper Networks Junos OS Evolved versions prior to 19.3R1-EVO.

Juniper SIRT is not aware of any malicious exploitation of these vulnerabilities.

These issues were discovered during external security research.

These issues are also known as SACK Slowness SACK Panic.

Important security issues resolved include:

CVE CVSS Summary
CVE-2019-11477 7.5 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) 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.
CVE-2019-11478 7.5 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) 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.
CVE-2019-11479 7.5 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) 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.
Solution:

The following software releases have been updated to resolve these specific issues: Junos OS Evolved 19.3R1 and all subsequent releases.

These issues are being tracked as 1455121.

Workaround:

There are no viable workarounds for these issues.

To reduce the risk of malicious exploitation, use access lists or firewall filters to limit CLI access to the device only from trusted, administrative networks or hosts. Additionally, limit access to the Junos OS Evolved shell to only trusted system administrators.

Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
 
Modification History:
2021-07-14: Initial Publication.

CVSS Score:
8.2 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H)
Severity Level:
High
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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