-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NetBSD Security Advisory 2018-004 ================================= Topic: Remote Memory Corruption in IPv6 Version: NetBSD-current: source prior to Tue, Jan 30th 2018 NetBSD 7.1 - 7.1.1: affected NetBSD 7.0 - 7.0.2: affected NetBSD 6.1 - 6.1.4: affected NetBSD 6.0 - 6.0.5: affected Severity: Remote DoS, Remote Memory Corruption Fixed: NetBSD-current: Tue, Jan 30th 2018 NetBSD-7-1 branch: Tue, Jan 30th 2018 NetBSD-7-0 branch: Tue, Jan 30th 2018 NetBSD-7 branch: Tue, Jan 30th 2018 NetBSD-6-1 branch: Tue, Jan 30th 2018 NetBSD-6-0 branch: Tue, Jan 30th 2018 NetBSD-6 branch: Tue, Jan 30th 2018 Teeny versions released later than the fix date will contain the fix. Please note that NetBSD releases prior to 6.0 are no longer supported. It is recommended that all users upgrade to a supported release. Abstract ======== A mistake in the way received IPv6 packets are handled allowed an attacker to remotely trigger a memory corruption. Technical Details ================= When a packet is received, the kernel stores it in memory as chain of mbufs. An mbuf is basically a block of contiguous memory. A function, located deep into the IPv6 entry point, was not performing the necessary checks when treating a received IPv6 packet. It was parsing the IPv6 options assuming they were located in the first mbuf of the chain, but this assumption was incorrect. Therefore, it was possible for this function to return a pointer that pointed to an area located after the first mbuf. This pointer was then either read from, or written to with one byte that could be controlled by the packet. It has been demonstrated that by sending a special combination of nested IPv6 fragments, this bug could be exploited remotely, and could allow an attacker to cause the kernel to behave unexpectedly because random areas of memory were overwritten. It is not clear whether this attack could be turned to a code execution attack. The PF firewall can mitigate this particular attack, because it rejects nested IPv6 fragments by default. NPF does not reject such fragments by default. The status of IPF in this regard has not been investigated. It is possible that other vectors than IPv6 fragments could trigger this vulnerability. Solutions and Workarounds ========================= For all NetBSD versions, you need to obtain fixed kernel sources, rebuild and install the new kernel, and reboot the system. The fixed source may be obtained from the NetBSD CVS repository. The following instructions briefly summarize how to upgrade your kernel. In these instructions, replace: ARCH with your architecture (from uname -m), KERNCONF with the name of your kernel configuration file and VERSION with the file version below File versions containing the fixes: FILE HEAD netbsd-7 netbsd-7-0 netbsd-7-1 ---- ---- -------- ---------- ---------- src/sys/netinet6/frag6.c 1.65 1.55.4.1 1.55.6.1 1.55.10.1 src/sys/netinet6/ip6_input.c 1.187 1.149.2.2 1.149.2.1.2.1 1.149.2.1.6.1 src/sys/netinet6/ip6_var.h 1.78 1.62.2.2 1.62.2.1.2.1 1.62.2.1.6.1 src/sys/netinet6/raw_ip6.c 1.160 1.136.2.2 1.136.6.1 1.136.2.1.2.1 FILE netbsd-6 netbsd-6-0 netbsd-6-1 ---- -------- ---------- ---------- src/sys/netinet6/frag6.c 1.52.2.3 1.52.2.1.4.2 1.52.2.2.2.1 src/sys/netinet6/ip6_input.c 1.136.2.2 1.136.6.2 1.136.8.2 src/sys/netinet6/ip6_var.h 1.58.2.2 1.58.6.2 1.58.8.2 src/sys/netinet6/raw_ip6.c 1.109.2.1 1.109.6.1 1.109.8.1 src/sys/netinet6/ah_input.c 1.59.8.1 1.59.12.1 1.59.14.1 src/sys/netinet6/esp_input.c 1.50.8.1 1.50.12.1 1.50.14.1 src/sys/netinet6/ipcomp_input.c 1.38.8.1 1.38.12.1 1.38.14.1 Note: for NetBSD-6, there are three more files that contain the fix. To update from CVS, re-build, and re-install the kernel: # cd src # cvs update -d -P -r VERSION sys/netinet6/frag6.c # cvs update -d -P -r VERSION sys/netinet6/ip6_input.c # cvs update -d -P -r VERSION sys/netinet6/ip6_var.h # cvs update -d -P -r VERSION sys/netinet6/raw_ip6.c If you run NetBSD-6: # cvs update -d -P -r VERSION sys/netinet6/ah_input.c # cvs update -d -P -r VERSION sys/netinet6/esp_input.c # cvs update -d -P -r VERSION sys/netinet6/ipcomp_input.c # ./build.sh kernel=KERNCONF # mv /netbsd /netbsd.old # cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd # shutdown -r now For more information on how to do this, see: http://www.NetBSD.org/guide/en/chap-kernel.html Thanks To ========= Maxime Villard for finding and fixing the issue. Revision History ================ 2018-02-12 Initial release 2018-03-09 Note that NetBSD 7.1.1 is affected More Information ================ Advisories may be updated as new information becomes available. The most recent version of this advisory (PGP signed) can be found at http://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2018-0XX.txt.asc Information about NetBSD and NetBSD security can be found at http://www.NetBSD.org/ and http://www.NetBSD.org/Security/ . Copyright 2018, The NetBSD Foundation, Inc. All Rights Reserved. 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