{"id":"AZL-83351","summary":"CVE-2026-31503 affecting package kernel for versions less than 6.6.134.1-2","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nudp: Fix wildcard bind conflict check when using hash2\n\nWhen binding a udp_sock to a local address and port, UDP uses\ntwo hashes (udptable-\u003ehash and udptable-\u003ehash2) for collision\ndetection. The current code switches to \"hash2\" when\nhslot-\u003ecount \u003e 10.\n\n\"hash2\" is keyed by local address and local port.\n\"hash\" is keyed by local port only.\n\nThe issue can be shown in the following bind sequence (pseudo code):\n\nbind(fd1,  \"[fd00::1]:8888\")\nbind(fd2,  \"[fd00::2]:8888\")\nbind(fd3,  \"[fd00::3]:8888\")\nbind(fd4,  \"[fd00::4]:8888\")\nbind(fd5,  \"[fd00::5]:8888\")\nbind(fd6,  \"[fd00::6]:8888\")\nbind(fd7,  \"[fd00::7]:8888\")\nbind(fd8,  \"[fd00::8]:8888\")\nbind(fd9,  \"[fd00::9]:8888\")\nbind(fd10, \"[fd00::10]:8888\")\n\n/* Correctly return -EADDRINUSE because \"hash\" is used\n * instead of \"hash2\". udp_lib_lport_inuse() detects the\n * conflict.\n */\nbind(fail_fd, \"[::]:8888\")\n\n/* After one more socket is bound to \"[fd00::11]:8888\",\n * hslot-\u003ecount exceeds 10 and \"hash2\" is used instead.\n */\nbind(fd11, \"[fd00::11]:8888\")\nbind(fail_fd, \"[::]:8888\")      /* succeeds unexpectedly */\n\nThe same issue applies to the IPv4 wildcard address \"0.0.0.0\"\nand the IPv4-mapped wildcard address \"::ffff:0.0.0.0\". For\nexample, if there are existing sockets bound to\n\"192.168.1.[1-11]:8888\", then binding \"0.0.0.0:8888\" or\n\"[::ffff:0.0.0.0]:8888\" can also miss the conflict when\nhslot-\u003ecount \u003e 10.\n\nTCP inet_csk_get_port() already has the correct check in\ninet_use_bhash2_on_bind(). Rename it to\ninet_use_hash2_on_bind() and move it to inet_hashtables.h\nso udp.c can reuse it in this fix.","modified":"2026-08-28T17:47:14.213849662Z","published":"2026-04-22T14:16:48Z","upstream":["CVE-2026-31503"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31503"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.134.1-2"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-83351.json"}}],"schema_version":"1.9.0"}