Re: [SECURITY] [DSA 4272-1] linux security update
On 14.08.18 21:52, Salvatore Bonaccorso wrote:
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
It seems that the thresholds should be applied in reverse order, the stretch
kernel complains if we try to shring the high threshold below the low one
(and is probably right).
For the stable distribution (stretch), this problem has been fixed in
(just a note for those who can't just reboot).
Matus UHLAR - fantomas, email@example.com ; http://www.fantomas.sk/
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