{"api_version":"1","generated_at":"2026-04-19T01:15:26+00:00","cve":"CVE-2026-23300","urls":{"html":"https://cve.report/CVE-2026-23300","api":"https://cve.report/api/cve/CVE-2026-23300.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-23300","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-23300"},"summary":{"title":"net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop\n\nWhen a standalone IPv6 nexthop object is created with a loopback device\n(e.g., \"ip -6 nexthop add id 100 dev lo\"), fib6_nh_init() misclassifies\nit as a reject route. This is because nexthop objects have no destination\nprefix (fc_dst=::), causing fib6_is_reject() to match any loopback\nnexthop. The reject path skips fib_nh_common_init(), leaving\nnhc_pcpu_rth_output unallocated. If an IPv4 route later references this\nnexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and\npanics.\n\nSimplify the check in fib6_nh_init() to only match explicit reject\nroutes (RTF_REJECT) instead of using fib6_is_reject(). The loopback\npromotion heuristic in fib6_is_reject() is handled separately by\nip6_route_info_create_nh(). After this change, the three cases behave\nas follows:\n\n1. Explicit reject route (\"ip -6 route add unreachable 2001:db8::/64\"):\n   RTF_REJECT is set, enters reject path, skips fib_nh_common_init().\n   No behavior change.\n\n2. Implicit loopback reject route (\"ip -6 route add 2001:db8::/32 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. ip6_route_info_create_nh() still promotes it to reject\n   afterward. nhc_pcpu_rth_output is allocated but unused, which is\n   harmless.\n\n3. Standalone nexthop object (\"ip -6 nexthop add id 100 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. nhc_pcpu_rth_output is properly allocated, fixing the crash\n   when IPv4 routes reference this nexthop.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-03-25 11:16:25","updated_at":"2026-04-18 09:16:17"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9","name":"https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a","name":"https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c","name":"https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc","name":"https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133","name":"https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f","name":"https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644","name":"https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093","name":"https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-23300","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23300","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 493ced1ac47c48bb86d9d4e8e87df8592be85a0e 607e68c1b7c5a30c795571be1906d716e989a644 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 493ced1ac47c48bb86d9d4e8e87df8592be85a0e c11d7c56c2076ee9cd72004f1976fe0734df2ae9 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 493ced1ac47c48bb86d9d4e8e87df8592be85a0e b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 493ced1ac47c48bb86d9d4e8e87df8592be85a0e b299121e7453d23faddf464087dff513a495b4fc git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.203 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.167 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.130 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.77 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.17 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.7 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"23300","cve":"CVE-2026-23300","epss":"0.000320000","percentile":"0.090980000","score_date":"2026-04-18","updated_at":"2026-04-19 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the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop\n\nWhen a standalone IPv6 nexthop object is created with a loopback device\n(e.g., \"ip -6 nexthop add id 100 dev lo\"), fib6_nh_init() misclassifies\nit as a reject route. This is because nexthop objects have no destination\nprefix (fc_dst=::), causing fib6_is_reject() to match any loopback\nnexthop. The reject path skips fib_nh_common_init(), leaving\nnhc_pcpu_rth_output unallocated. If an IPv4 route later references this\nnexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and\npanics.\n\nSimplify the check in fib6_nh_init() to only match explicit reject\nroutes (RTF_REJECT) instead of using fib6_is_reject(). The loopback\npromotion heuristic in fib6_is_reject() is handled separately by\nip6_route_info_create_nh(). After this change, the three cases behave\nas follows:\n\n1. Explicit reject route (\"ip -6 route add unreachable 2001:db8::/64\"):\n   RTF_REJECT is set, enters reject path, skips fib_nh_common_init().\n   No behavior change.\n\n2. Implicit loopback reject route (\"ip -6 route add 2001:db8::/32 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. ip6_route_info_create_nh() still promotes it to reject\n   afterward. nhc_pcpu_rth_output is allocated but unused, which is\n   harmless.\n\n3. Standalone nexthop object (\"ip -6 nexthop add id 100 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. nhc_pcpu_rth_output is properly allocated, fixing the crash\n   when IPv4 routes reference this nexthop."}],"providerMetadata":{"dateUpdated":"2026-04-18T08:57:47.517Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644"},{"url":"https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9"},{"url":"https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a"},{"url":"https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc"},{"url":"https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f"},{"url":"https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c"},{"url":"https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133"},{"url":"https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093"}],"title":"net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-23300","datePublished":"2026-03-25T10:26:56.138Z","dateReserved":"2026-01-13T15:37:45.993Z","dateUpdated":"2026-04-18T08:57:47.517Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-03-25 11:16:25","lastModifiedDate":"2026-04-18 09:16:17","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"23300","Ordinal":"1","Title":"net: ipv6: fix panic when IPv4 route references loopback IPv6 ne","CVE":"CVE-2026-23300","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"23300","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop\n\nWhen a standalone IPv6 nexthop object is created with a loopback device\n(e.g., \"ip -6 nexthop add id 100 dev lo\"), fib6_nh_init() misclassifies\nit as a reject route. This is because nexthop objects have no destination\nprefix (fc_dst=::), causing fib6_is_reject() to match any loopback\nnexthop. The reject path skips fib_nh_common_init(), leaving\nnhc_pcpu_rth_output unallocated. If an IPv4 route later references this\nnexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and\npanics.\n\nSimplify the check in fib6_nh_init() to only match explicit reject\nroutes (RTF_REJECT) instead of using fib6_is_reject(). The loopback\npromotion heuristic in fib6_is_reject() is handled separately by\nip6_route_info_create_nh(). After this change, the three cases behave\nas follows:\n\n1. Explicit reject route (\"ip -6 route add unreachable 2001:db8::/64\"):\n   RTF_REJECT is set, enters reject path, skips fib_nh_common_init().\n   No behavior change.\n\n2. Implicit loopback reject route (\"ip -6 route add 2001:db8::/32 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. ip6_route_info_create_nh() still promotes it to reject\n   afterward. nhc_pcpu_rth_output is allocated but unused, which is\n   harmless.\n\n3. Standalone nexthop object (\"ip -6 nexthop add id 100 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. nhc_pcpu_rth_output is properly allocated, fixing the crash\n   when IPv4 routes reference this nexthop.","Type":"Description","Title":"net: ipv6: fix panic when IPv4 route references loopback IPv6 ne"}]}}}