{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2025-38472", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2025-38472", "idYear": 2025, "status": "PUBLISHED", "publishedAt": "2025-07-28T11:21:33.977Z", "updatedAt": "2026-10-15T21:52:17.084Z", "importedAt": "2026-10-24T01:57:34.152Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "netfilter: nf_conntrack: fix crash due to removal of uninitialised entry", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack: fix crash due to removal of uninitialised entry\n\nA crash in conntrack was reported while trying to unlink the conntrack\nentry from the hash bucket list:\n [exception RIP: __nf_ct_delete_from_lists+172]\n [..]\n #7 [ff539b5a2b043aa0] nf_ct_delete at ffffffffc124d421 [nf_conntrack]\n #8 [ff539b5a2b043ad0] nf_ct_gc_expired at ffffffffc124d999 [nf_conntrack]\n #9 [ff539b5a2b043ae0] __nf_conntrack_find_get at ffffffffc124efbc [nf_conntrack]\n [..]\n\nThe nf_conn struct is marked as allocated from slab but appears to be in\na partially initialised state:\n\n ct hlist pointer is garbage; looks like the ct hash value\n (hence crash).\n ct->status is equal to IPS_CONFIRMED|IPS_DYING, which is expected\n ct->timeout is 30000 (=30s), which is unexpected.\n\nEverything else looks like normal udp conntrack entry. If we ignore\nct->status and pretend its 0, the entry matches those that are newly\nallocated but not yet inserted into the hash:\n - ct hlist pointers are overloaded and store/cache the raw tuple hash\n - ct->timeout matches the relative time expected for a new udp flow\n rather than the absolute 'jiffies' value.\n\nIf it were not for the presence of IPS_CONFIRMED,\n__nf_conntrack_find_get() would have skipped the entry.\n\nTheory is that we did hit following race:\n\ncpu x \t\t\tcpu y\t\t\tcpu z\n found entry E\t\tfound entry E\n E is expired\t\t\n nf_ct_delete()\n return E to rcu slab\n\t\t\t\t\tinit_conntrack\n\t\t\t\t\tE is re-inited,\n\t\t\t\t\tct->status set to 0\n\t\t\t\t\treply tuplehash hnnode.pprev\n\t\t\t\t\tstores hash value.\n\ncpu y found E right before it was deleted on cpu x.\nE is now re-inited on cpu z. cpu y was preempted before\nchecking for expiry and/or confirm bit.\n\n\t\t\t\t\t->refcnt set to 1\n\t\t\t\t\tE now owned by skb\n\t\t\t\t\t->timeout set to 30000\n\nIf cpu y were to resume now, it would observe E as\nexpired but would skip E due to missing CONFIRMED bit.\n\n\t\t\t\t\tnf_conntrack_confirm gets called\n\t\t\t\t\tsets: ct->status |= CONFIRMED\n\t\t\t\t\tThis is wrong: E is not yet added\n\t\t\t\t\tto hashtable.\n\ncpu y resumes, it observes E as expired but CONFIRMED:\n\t\t\t\n\t\t\tnf_ct_expired()\n\t\t\t -> yes (ct->timeout is 30s)\n\t\t\tconfirmed bit set.\n\ncpu y will try to delete E from the hashtable:\n\t\t\tnf_ct_delete() -> set DYING bit\n\t\t\t__nf_ct_delete_from_lists\n\nEven this scenario doesn't guarantee a crash:\ncpu z still holds the table bucket lock(s) so y blocks:\n\n\t\t\twait for spinlock held by z\n\n\t\t\t\t\tCONFIRMED is set but there is no\n\t\t\t\t\tguarantee ct will be added to hash:\n\t\t\t\t\t\"chaintoolong\" or \"clash resolution\"\n\t\t\t\t\tlogic both skip the insert step.\n\t\t\t\t\treply hnnode.pprev still stores the\n\t\t\t\t\thash value.\n\n\t\t\t\t\tunlocks spinlock\n\t\t\t\t\treturn NF_DROP\n\t\t\t\n\nIn case CPU z does insert the entry into the hashtable, cpu y will unlink\nE again right away but no crash occurs.\n\nWithout 'cpu y' race, 'garbage' hlist is of no consequence:\nct refcnt remains at 1, eventually skb will be free'd and E gets\ndestroyed via: nf_conntrack_put -> nf_conntrack_destroy -> nf_ct_destroy.\n\nTo resolve this, move the IPS_CONFIRMED assignment after the table\ninsertion but before the unlock.\n\nPablo points out that the confirm-bit-store could be reordered to happen\nbefore hlist add resp. the timeout fixup, so switch to set_bit and\nbefore_atomic memory barrier to prevent this.\n\nIt doesn't matter if other CPUs can observe a newly inserted entry right\nbefore the CONFIRMED bit was set:\n\nSuch event cannot be distinguished from above \"E is the old incarnation\"\ncase: the entry will be skipped.\n\nAlso change nf_ct_should_gc() to first check the confirmed bit.\n\nThe gc sequence is:\n 1. Check if entry has expired, if not skip to next entry\n 2. Obtain a reference to the expired entry.\n 3. Call nf_ct_should_gc() to double-check step 1.\n\nnf_ct_should_gc() is thus called only for entries that already failed an\nexpiry check. After this patch, once the confirmed bit check pas\n---truncated---", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "1397af5bfd7d32b0cf2adb70a78c9a9e8f11d912", "status": "affected", "versionType": "git", "lessThan": "a47ef874189d47f934d0809ae738886307c0ea22" }, { "version": "1397af5bfd7d32b0cf2adb70a78c9a9e8f11d912", "status": "affected", "versionType": "git", "lessThan": "76179961c423cd698080b5e4d5583cf7f4fcdde9" }, { "version": "1397af5bfd7d32b0cf2adb70a78c9a9e8f11d912", "status": "affected", "versionType": "git", "lessThan": "fc38c249c622ff5e3011b8845fd49dbfd9289afc" }, { "version": "1397af5bfd7d32b0cf2adb70a78c9a9e8f11d912", "status": "affected", "versionType": "git", "lessThan": "938ce0e8422d3793fe30df2ed0e37f6bc0598379" }, { "version": "1397af5bfd7d32b0cf2adb70a78c9a9e8f11d912", "status": "affected", "versionType": "git", "lessThan": "2d72afb340657f03f7261e9243b44457a9228ac7" }, { "version": "594cea2c09f7cd440d1ee1c4547d5bc6a646b0e4", "status": "affected", "versionType": "git" }, { "version": "5.18.13", "status": "affected", "versionType": "semver", "lessThan": "5.19" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "5.19", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "5.19" }, { "version": "6.1.147", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.100", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.40", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.15.8", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.15.*" }, { "version": "6.16", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }