cbcvebase.
CVE-2018-5391
published 2018-09-06

CVE-2018-5391: The Linux kernel, versions 3.9+, is vulnerable to a denial of service attack with low rates of specially modified packets targeting IP fragment re-assembly. An…

PriorityP183high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
ITWVulnCheck KEVRansomware
Exploited in the wild
EPSS
24.57%
97.6th percentile
The Linux kernel, versions 3.9+, is vulnerable to a denial of service attack with low rates of specially modified packets targeting IP fragment re-assembly. An attacker may cause a denial of service condition by sending specially crafted IP fragments. Various vulnerabilities in IP fragmentation have been discovered and fixed over the years. The current vulnerability (CVE-2018-5391) became exploitable in the Linux kernel with the increase of the IP fragment reassembly queue size.

Affected

133 ranges· showing 25
VendorProductVersion rangeFixed in
canonicalubuntu_linux
canonicalubuntu_linux
canonicalubuntu_linux
canonicalubuntu_linux
debiandebian_linux
debiandebian_linux
debianlinux< linux 4.17.15-1 (bookworm)linux 4.17.15-1 (bookworm)
f5big-ip_access_policy_manager>= 11.5.1 < 11.6.5.111.6.5.1
f5big-ip_access_policy_manager>= 12.1.0 < 12.1.512.1.5
f5big-ip_access_policy_manager>= 13.0.0 < 13.1.313.1.3
f5big-ip_access_policy_manager>= 14.0.0 < 14.0.1.114.0.1.1
f5big-ip_access_policy_manager>= 14.1.0 < 14.1.2.414.1.2.4
f5big-ip_advanced_firewall_manager>= 11.5.1 < 11.6.5.111.6.5.1
f5big-ip_advanced_firewall_manager>= 12.1.0 < 12.1.512.1.5
f5big-ip_advanced_firewall_manager>= 13.0.0 < 13.1.313.1.3
f5big-ip_advanced_firewall_manager>= 14.0.0 < 14.0.1.114.0.1.1
f5big-ip_advanced_firewall_manager>= 14.1.0 < 14.1.2.414.1.2.4
f5big-ip_analytics>= 11.5.1 < 11.6.5.111.6.5.1
f5big-ip_analytics>= 12.1.0 < 12.1.512.1.5
f5big-ip_analytics>= 13.0.0 < 13.1.313.1.3
f5big-ip_analytics>= 14.0.0 < 14.0.1.114.0.1.1
f5big-ip_analytics>= 14.1.0 < 14.1.2.414.1.2.4
f5big-ip_application_acceleration_manager>= 11.5.1 < 11.6.5.111.6.5.1
f5big-ip_application_acceleration_manager>= 12.1.0 < 12.1.512.1.5
f5big-ip_application_acceleration_manager>= 13.0.0 < 13.1.313.1.3

Detection & IOCsextracted from sources · hover to see the quote

  • Detect FragmentSmack DoS: look for high rates of incoming IP fragment packets (IPv4 and IPv6) targeting a host, especially with randomly or specially crafted fragment offsets designed to trigger expensive reassembly algorithms and cause CPU saturation.
  • Monitor kernel sysctl values net.ipv4.ipfrag_high_thresh and net.ipv4.ipfrag_low_thresh (and IPv6 counterparts net.ipv6.ipfrag_high_thresh / net.ipv6.ipfrag_low_thresh); default values of 4MB/3MB indicate an unmitigated system. Mitigated systems should show 262144 (256 kB) / 196608 (192 kB) or lower.
  • Affected Linux kernel versions start at 3.9; systems running Linux kernel 3.9 or later that have not applied the fix (Debian: kernel 4.17.15-1) should be flagged as vulnerable.
  • For PAN-OS environments, the attack surface is limited to the Management Plane interface; monitor for unexpected fragmented traffic directed at the management interface of PAN-OS devices.
  • ·The vulnerability became exploitable due to an increase in the IP fragment reassembly queue size; the root cause is a configuration/kernel change, not just a code bug.
  • ·Lowering ipfrag_high_thresh to 256 kB limits the reassembly queue to only two 64K fragments simultaneously, which may break applications relying on large UDP packets.
  • ·RHEL 5 is affected but will not receive a fix due to end-of-life; RHEL 8 is not affected. Detection/patching scope should be adjusted accordingly.
  • ·PAN-OS affected versions span 6.1.21 and earlier, 7.1.19 and earlier, 8.0.12 and earlier, and 8.1.4 and earlier across multiple hardware platforms; fixed in PAN-OS 6.1.22, 7.1.20, 8.0.13, and 8.1.5 respectively.

CVSS provenance

nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv2.07.8HIGHAV:N/AC:L/Au:N/C:N/I:N/A:C
osv7.5HIGH
vulncheck7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
vendor_ubuntu5.6MEDIUM
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