{"id":"CVE-2026-31503","state":"PUBLISHED","title":"udp: Fix wildcard bind conflict check when using hash2","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.","publishedAt":"2026-04-22T13:54:23.221Z","updatedAt":"2026-10-15T01:16:42.154Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"d6ace0dbcbb7fd285738bb87b42b71b01858c952","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"2297e38114316b26ae02f2d205c49b5511c5ed55","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"f1bed05a832ae79be5f7a105da56810eaa59a5f1","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"0a360f7f73a06ac88f18917055fbcc79694252d7","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"e537dd15d0d4ad989d56a1021290f0c674dd8b28","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/inet_hashtables.h","net/ipv4/inet_connection_sock.c","net/ipv4/udp.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.33","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.33","versionType":"semver"},{"version":"6.1.168","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.131","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.80","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.21","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.11","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/inet_hashtables.h","net/ipv4/inet_connection_sock.c","net/ipv4/udp.c"]}],"references":["https://git.kernel.org/stable/c/d6ace0dbcbb7fd285738bb87b42b71b01858c952","https://git.kernel.org/stable/c/2297e38114316b26ae02f2d205c49b5511c5ed55","https://git.kernel.org/stable/c/f1bed05a832ae79be5f7a105da56810eaa59a5f1","https://git.kernel.org/stable/c/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4","https://git.kernel.org/stable/c/0a360f7f73a06ac88f18917055fbcc79694252d7","https://git.kernel.org/stable/c/e537dd15d0d4ad989d56a1021290f0c674dd8b28","https://cert-portal.siemens.com/productcert/html/ssa-082556.html","https://cert-portal.siemens.com/productcert/html/ssa-019113.html","https://cert-portal.siemens.com/productcert/html/ssa-457936.html"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31503.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31503","state":"PUBLISHED","datePublished":"2026-04-22T13:54:23.221Z","dateUpdated":"2026-10-15T01:16:42.154Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.105Z"},"containers":{"cna":{"title":"udp: Fix wildcard bind conflict check when using hash2","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"d6ace0dbcbb7fd285738bb87b42b71b01858c952","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"2297e38114316b26ae02f2d205c49b5511c5ed55","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"f1bed05a832ae79be5f7a105da56810eaa59a5f1","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"0a360f7f73a06ac88f18917055fbcc79694252d7","versionType":"git"},{"version":"30fff9231fad757c061285e347b33c5149c2c2e4","status":"affected","lessThan":"e537dd15d0d4ad989d56a1021290f0c674dd8b28","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/inet_hashtables.h","net/ipv4/inet_connection_sock.c","net/ipv4/udp.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.33","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.33","versionType":"semver"},{"version":"6.1.168","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.131","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.80","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.21","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.11","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/inet_hashtables.h","net/ipv4/inet_connection_sock.c","net/ipv4/udp.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/d6ace0dbcbb7fd285738bb87b42b71b01858c952"},{"url":"https://git.kernel.org/stable/c/2297e38114316b26ae02f2d205c49b5511c5ed55"},{"url":"https://git.kernel.org/stable/c/f1bed05a832ae79be5f7a105da56810eaa59a5f1"},{"url":"https://git.kernel.org/stable/c/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4"},{"url":"https://git.kernel.org/stable/c/0a360f7f73a06ac88f18917055fbcc79694252d7"},{"url":"https://git.kernel.org/stable/c/e537dd15d0d4ad989d56a1021290f0c674dd8b28"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T22:10:00.326Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.1.168"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.6.131"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.12.80"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.18.21"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"6.19.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.33","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"affected":[{"vendor":"Siemens","product":"SIMATIC 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