{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-23300", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:45.993Z", "datePublished": "2026-03-25T10:26:56.138Z", "dateUpdated": "2026-03-25T10:26:56.138Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-03-25T10:26:56.138Z"}, "descriptions": [{"lang": "en", "value": "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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/ipv6/route.c"], "versions": [{"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e", "lessThan": "b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a", "status": "affected", "versionType": "git"}, {"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e", "lessThan": "b299121e7453d23faddf464087dff513a495b4fc", "status": "affected", "versionType": "git"}, {"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e", "lessThan": "f7c9f8e3607440fe39300efbaf46cf7b5eecb23f", "status": "affected", "versionType": "git"}, {"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e", "lessThan": "b3b5a037d520afe3d5276e653bc0ff516bbda34c", "status": "affected", "versionType": "git"}, {"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e", "lessThan": "8650db85b4259d2885d2a80fbc2317ce24194133", "status": "affected", "versionType": "git"}, {"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e", "lessThan": "21ec92774d1536f71bdc90b0e3d052eff99cf093", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/ipv6/route.c"], "versions": [{"version": "5.3", "status": "affected"}, {"version": "0", "lessThan": "5.3", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.167", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.130", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.77", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.17", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.7", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0-rc3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.1.167"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.6.130"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.12.77"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.18.17"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.19.7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "7.0-rc3"}]}]}], "references": [{"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"}}}}

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{"cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-23300", "lastModified": "2026-03-25T11:16:25.623", "metrics": {}, "published": "2026-03-25T11:16:25.623", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{}

{}