Scientific Linux Security Update : kernel on SL6.x i386/x86_64 (20190617) (SACK Panic) (SACK Slowness)
High Nessus Plugin ID 125980
SynopsisThe remote Scientific Linux host is missing one or more security updates.
DescriptionSecurity Fix(es) :
- An integer overflow flaw was found in the way the Linux kernel's networking subsystem processed TCP Selective Acknowledgment (SACK) segments. While processing SACK segments, the Linux kernel's socket buffer (SKB) data structure becomes fragmented. Each fragment is about TCP maximum segment size (MSS) bytes. To efficiently process SACK blocks, the Linux kernel merges multiple fragmented SKBs into one, potentially overflowing the variable holding the number of segments. A remote attacker could use this flaw to crash the Linux kernel by sending a crafted sequence of SACK segments on a TCP connection with small value of TCP MSS, resulting in a denial of service (DoS). (CVE-2019-11477)
- kernel: Double free in lib/idr.c (CVE-2019-3896)
- Kernel: tcp: excessive resource consumption while processing SACK blocks allows remote denial of service (CVE-2019-11478)
- Kernel: tcp: excessive resource consumption for TCP connections with low MSS allows remote denial of service (CVE-2019-11479)
Bug Fix(es) :
- MDS mitigations not enabled on Intel Skylake CPUs
- kernel does not disable SMT with mds=full,nosmt
- md_clear flag missing from /proc/cpuinfo
SolutionUpdate the affected packages.