{"cve":"CVE-2026-31503","nvd":{"published":"2026-04-22T14:16:48.863","modified":"2026-10-15T02:19:08.900","status":"Modified","description":"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->hash and udptable->hash2) for collision\ndetection. The current code switches to \"hash2\" when\nhslot->count > 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->count 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->count > 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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/0a360f7f73a06ac88f18917055fbcc79694252d7","https://git.kernel.org/stable/c/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4","https://git.kernel.org/stable/c/2297e38114316b26ae02f2d205c49b5511c5ed55","https://git.kernel.org/stable/c/d6ace0dbcbb7fd285738bb87b42b71b01858c952","https://git.kernel.org/stable/c/e537dd15d0d4ad989d56a1021290f0c674dd8b28"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:30:49.762551342+00:00"},"epss":{"cve":"CVE-2026-31503","score":0.00125,"percentile":0.02207,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}