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Debian Security Advisory DSA-4272-1                   security@debian.org
https://www.debian.org/security/                     Salvatore Bonaccorso
August 14, 2018                       https://www.debian.org/security/faq
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Package        : linux
CVE ID         : CVE-2018-5391

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

    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:
https://security-tracker.debian.org/tracker/linux

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://www.debian.org/security/

Mailing list: debian-security-announce@lists.debian.org