{"cvss":5.5,"datePublished":"2026-04-22T14:16:48.863","dateUpdated":"2026-11-05T22:18:36.067","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.","id":"CVE-2026-31503","raw":{"affected":[{"affectedData":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["include/net/inet_hashtables.h","net/ipv4/inet_connection_sock.c","net/ipv4/udp.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"d6ace0dbcbb7fd285738bb87b42b71b01858c952","status":"affected","version":"30fff9231fad757c061285e347b33c5149c2c2e4","versionType":"git"},{"lessThan":"2297e38114316b26ae02f2d205c49b5511c5ed55","status":"affected","version":"30fff9231fad757c061285e347b33c5149c2c2e4","versionType":"git"},{"lessThan":"f1bed05a832ae79be5f7a105da56810eaa59a5f1","status":"affected","version":"30fff9231fad757c061285e347b33c5149c2c2e4","versionType":"git"},{"lessThan":"18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4","status":"affected","version":"30fff9231fad757c061285e347b33c5149c2c2e4","versionType":"git"},{"lessThan":"0a360f7f73a06ac88f18917055fbcc79694252d7","status":"affected","version":"30fff9231fad757c061285e347b33c5149c2c2e4","versionType":"git"},{"lessThan":"e537dd15d0d4ad989d56a1021290f0c674dd8b28","status":"affected","version":"30fff9231fad757c061285e347b33c5149c2c2e4","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["include/net/inet_hashtables.h","net/ipv4/inet_connection_sock.c","net/ipv4/udp.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"2.6.33"},{"lessThan":"2.6.33","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.168","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.131","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.80","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.21","versionType":"semver"},{"lessThanOrEqual":"6.19.*","status":"unaffected","version":"6.19.11","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.0","versionType":"original_commit_for_fix"}]}],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"affectedData":[{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.5","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.5","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.5","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.5","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.6","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.5","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]}],"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"configurations":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"8311CDFC-9254-42F8-B327-8390CCD33713","versionEndExcluding":"6.1.168","versionStartIncluding":"2.6.33.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"CE6ED4D4-0046-4573-BFA9-D64143B6A89F","versionEndExcluding":"6.6.131","versionStartIncluding":"6.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6","versionEndExcluding":"6.12.80","versionStartIncluding":"6.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"ED39847A-3B46-4729-B7CA-B2C30B9FA8FE","versionEndExcluding":"6.18.21","versionStartIncluding":"6.13","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"4CA2E747-A9EC-4518-9AA2-B4247FC748B7","versionEndExcluding":"6.19.11","versionStartIncluding":"6.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:2.6.33:-:*:*:*:*:*:*","matchCriteriaId":"EF818826-D9F2-42F9-9638-9609513561A3","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*","matchCriteriaId":"F253B622-8837-4245-BCE5-A7BF8FC76A16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*","matchCriteriaId":"4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*","matchCriteriaId":"F666C8D8-6538-46D4-B318-87610DE64C34","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*","matchCriteriaId":"02259FDA-961B-47BC-AE7F-93D7EC6E90C2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*","matchCriteriaId":"58A9FEFF-C040-420D-8F0A-BFDAAA1DF258","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*","matchCriteriaId":"1D2315C0-D46F-4F85-9754-F9E5E11374A6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*","matchCriteriaId":"512EE3A8-A590-4501-9A94-5D4B268D6138","vulnerable":true}],"negate":false,"operator":"OR"}]}],"cveTags":[],"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."}],"id":"CVE-2026-31503","lastModified":"2026-11-05T22:18:36.067","metrics":{"cvssMetricV31":[{"cvssData":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":5.5,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"exploitabilityScore":1.8,"impactScore":3.6,"source":"nvd@nist.gov","type":"Primary"}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"id":"CVE-2026-31503","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","timestamp":"2026-11-05T21:36:04.666647Z","version":"2.0.3"}}]},"published":"2026-04-22T14:16:48.863","references":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/0a360f7f73a06ac88f18917055fbcc79694252d7"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/2297e38114316b26ae02f2d205c49b5511c5ed55"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/d6ace0dbcbb7fd285738bb87b42b71b01858c952"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/e537dd15d0d4ad989d56a1021290f0c674dd8b28"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/f1bed05a832ae79be5f7a105da56810eaa59a5f1"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}],"sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","vulnStatus":"Modified","weaknesses":[{"description":[{"lang":"en","value":"NVD-CWE-noinfo"}],"source":"nvd@nist.gov","type":"Primary"}]},"severity":"MEDIUM","source":"nvd","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nudp: Fix wildcard bind conflict check when using..."}