Debian Security Advisory

DSA-4272-1 linux -- security update

Date Reported:
14 Aug 2018
Affected Packages:
Security database references:
In Mitre's CVE dictionary: CVE-2018-5391.
More information:
  • CVE-2018-5391 (FragmentSmack)

    Juha-Matti Tilli discovered a flaw in the way the Linux kernel handled reassembly of fragmented IPv4 and IPv6 packets. A remote attacker can take advantage of this flaw to trigger time and calculation expensive fragment reassembly algorithms by sending specially crafted packets, leading to remote denial of service.

    This is mitigated by reducing the default limits on memory usage for incomplete fragmented packets. The same mitigation can be achieved without the need to reboot, by setting the sysctls:

    net.ipv4.ipfrag_low_thresh = 196608
    net.ipv6.ip6frag_low_thresh = 196608
    net.ipv4.ipfrag_high_thresh = 262144
    net.ipv6.ip6frag_high_thresh = 262144

    The default values may still be increased by local configuration if necessary.

For the stable distribution (stretch), this problem has been fixed in version 4.9.110-3+deb9u2.

We recommend that you upgrade your linux packages.

For the detailed security status of linux please refer to its security tracker page at: