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vuln-cve/data/2025/21xxx/CVE-2025-21637.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2025-21637",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2024-12-29T08:45:45.726Z",
"datePublished": "2025-01-19T10:17:55.321Z",
"dateUpdated": "2026-08-05T11:53:17.199Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux",
"dateUpdated": "2026-08-05T11:53:17.199Z"
},
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: sysctl: udp_port: avoid using current->nsproxy\n\nAs mentioned in a previous commit of this series, using the 'net'\nstructure via 'current' is not recommended for different reasons:\n\n- Inconsistency: getting info from the reader's/writer's netns vs only\n from the opener's netns.\n\n- current->nsproxy can be NULL in some cases, resulting in an 'Oops'\n (null-ptr-deref), e.g. when the current task is exiting, as spotted by\n syzbot [1] using acct(2).\n\nThe 'net' structure can be obtained from the table->data using\ncontainer_of().\n\nNote that table->data could also be used directly, but that would\nincrease the size of this fix, while 'sctp.ctl_sock' still needs to be\nretrieved from 'net' structure."
}
],
"metrics": [
{
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
"baseScore": 7.1,
"baseSeverity": "HIGH"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - Despite living in net/sctp/, the vulnerable function is a procfs sysctl ->proc_handler reachable only through local file I/O on /proc/sys/net/sctp/udp_port and local syscalls (acct(2), write(2)); no received SCTP or UDP packet ever reaches it.\nAC:L - Both trigger paths are fully deterministic and entirely attacker-driven — either unshare/open/SCM_RIGHTS/write for the netns-confusion path, or acct(2) plus `umount -l` plus process exit for the NULL deref — with no race, no victim state, and no memory-layout dependency.\nPR:L - An unprivileged user can reach the flaw via `unshare -Urn`, since cap_capable() grants the owner of a child user namespace CAP_NET_ADMIN over it (security/commoncap.c:92), letting a process still in the init netns write through the child's sysctl fd and have the handler act on init_net; no real root is needed for that path.\nUI:N - The attacker performs every step from its own cooperating processes — namespace creation, fd passing, the write, or its own exit — with no action required from any other user or administrator.\nS:U - The flawed code and the affected resources are both kernel network-namespace state within the same kernel security authority; no hypervisor, IOMMU, or VM boundary is crossed.\nC:N - The NULL+offset dereference faults before returning any data, and the read side of the netns confusion only reports the caller's own netns value for a world-readable (0644) setting, so no protected information is disclosed.\nI:H - The netns confusion lets an unprivileged local user write init_net.sctp.udp_port and drive sctp_udp_sock_stop()/sctp_udp_sock_start() on the host namespace, fully controlling whether and on which port the host kernel decapsulates SCTP from UDP — an attacker-chosen modification of protected host network state and a bypass of SCTP packet filtering.\nA:H - The NULL-ptr-deref oops fires inside do_exit() while acct->lock is held, wedging the exiting task with a stuck mutex and pinned mount and panicking outright on panic_on_oops builds; separately, the cross-netns write destroys the host's SCTP UDP tunnel sockets, severing SCTP-over-UDP connectivity."
}
]
}
],
"affected": [
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"net/sctp/sysctl.c"
],
"versions": [
{
"version": "046c052b475e7119b6a30e3483e2888fc606a2f8",
"lessThan": "0a0966312ac3eedd7f5f2a766ed4702df39a9a65",
"status": "affected",
"versionType": "git"
},
{
"version": "046c052b475e7119b6a30e3483e2888fc606a2f8",
"lessThan": "e919197fb8616331f5dc81e4c3cc3d12769cb725",
"status": "affected",
"versionType": "git"
},
{
"version": "046c052b475e7119b6a30e3483e2888fc606a2f8",
"lessThan": "55627918febdf9d71107a1e68d1528dc591c9a15",
"status": "affected",
"versionType": "git"
},
{
"version": "046c052b475e7119b6a30e3483e2888fc606a2f8",
"lessThan": "5b77d73f3be5102720fb685b9e6900e3500e1096",
"status": "affected",
"versionType": "git"
},
{
"version": "046c052b475e7119b6a30e3483e2888fc606a2f8",
"lessThan": "c10377bbc1972d858eaf0ab366a311b39f8ef1b6",
"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/sctp/sysctl.c"
],
"versions": [
{
"version": "5.11",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.11",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "5.15.177",
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.1.125",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.6.72",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.12.10",
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.13",
"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": "5.11",
"versionEndExcluding": "5.15.177"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.11",
"versionEndExcluding": "6.1.125"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.11",
"versionEndExcluding": "6.6.72"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.11",
"versionEndExcluding": "6.12.10"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.11",
"versionEndExcluding": "6.13"
}
]
}
]
}
],
"references": [
{
"url": "https://git.kernel.org/stable/c/0a0966312ac3eedd7f5f2a766ed4702df39a9a65"
},
{
"url": "https://git.kernel.org/stable/c/e919197fb8616331f5dc81e4c3cc3d12769cb725"
},
{
"url": "https://git.kernel.org/stable/c/55627918febdf9d71107a1e68d1528dc591c9a15"
},
{
"url": "https://git.kernel.org/stable/c/5b77d73f3be5102720fb685b9e6900e3500e1096"
},
{
"url": "https://git.kernel.org/stable/c/c10377bbc1972d858eaf0ab366a311b39f8ef1b6"
}
],
"title": "sctp: sysctl: udp_port: avoid using current->nsproxy",
"x_generator": {
"engine": "bippy-1.2.0"
}
},
"adp": [
{
"metrics": [
{
"cvssV3_1": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 5.5,
"attackVector": "LOCAL",
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "NONE"
}
},
{
"other": {
"type": "ssvc",
"content": {
"id": "CVE-2025-21637",
"role": "CISA Coordinator",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2025-10-01T19:54:10.551212Z"
}
}
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"type": "CWE",
"cweId": "CWE-476",
"description": "CWE-476 NULL Pointer Dereference"
}
]
}
],
"title": "CISA ADP Vulnrichment",
"providerMetadata": {
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP",
"dateUpdated": "2025-10-01T19:57:17.821Z"
}
},
{
"title": "CVE Program Container",
"references": [
{
"url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html"
}
],
"providerMetadata": {
"orgId": "af854a3a-2127-422b-91ae-364da2661108",
"shortName": "CVE",
"dateUpdated": "2025-11-03T20:58:15.076Z"
}
}
]
}
}