{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-39840", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.141Z", "datePublished": "2025-09-19T15:26:15.596Z", "dateUpdated": "2026-08-05T12:05:33.644Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:05:33.644Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\naudit: fix out-of-bounds read in audit_compare_dname_path()\n\nWhen a watch on dir=/ is combined with an fsnotify event for a\nsingle-character name directly under / (e.g., creating /a), an\nout-of-bounds read can occur in audit_compare_dname_path().\n\nThe helper parent_len() returns 1 for \"/\". In audit_compare_dname_path(),\nwhen parentlen equals the full path length (1), the code sets p = path + 1\nand pathlen = 1 - 1 = 0. The subsequent loop then dereferences\np[pathlen - 1] (i.e., p[-1]), causing an out-of-bounds read.\n\nFix this by adding a pathlen > 0 check to the while loop condition\nto prevent the out-of-bounds access.\n\n[PM: subject tweak, sign-off email fixes]" } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable code is reached only through the syscall audit context (`__audit_getname`/`__audit_inode_child`) or an fsnotify event on a locally-installed audit watch, both of which require issuing local syscalls such as symlink()/mkdir()/rename(). No network-facing kernel service (nfsd/ksmbd) builds audit name entries via getname(), so there is no remote path to the defect.\nAC:L - The attacker fully controls both inputs — an all-slash pathname argument and the basename of the created child — so the backwards walk past the start of the buffer is triggered deterministically on every attempt, with no race to win and no timing dependency. Padding the slash string to ≥EMBEDDED_NAME_MAX deterministically forces the string into a page-aligned names_cachep object, so even the page-boundary read is attacker-arranged.\nPR:L - Any unprivileged local user can call symlink(\"///…\", \"/tmp/x\") in a world-writable directory; no capability, namespace trick, or audit privilege is needed, and the AUDIT_TYPE_UNKNOWN found_child branch bypasses the ino/dev ownership check entirely. The only precondition is a system-wide audit ruleset installed by the administrator, which is an environmental condition rather than an attacker privilege.\nUI:N - The attacking process performs the whole sequence itself in a single syscall; no victim has to mount a filesystem, open a file, or take any other action.\nS:U - The out-of-bounds read occurs in kernel heap memory and both the flaw and its consequences stay within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - This is an out-of-bounds read that is not bounded to a few bytes — the loop keeps decrementing and dereferencing backwards for as long as the preceding kernel memory contains 0x2f bytes, so an attacker who sprays '/' bytes into the heap can extend the walk across adjacent slab objects and pages, touching arbitrary kernel memory beyond the allocation.\nI:N - The defect performs only reads; `pathlen` becomes negative so the comparison always returns \"no match\" and `memcmp()` is unreachable, leaving no memory write, no control-flow influence, and no change to the audit records that would be emitted.\nA:H - With a slash string long enough to occupy a page-aligned 4096-byte names_cachep object, the walk immediately dereferences the byte before a page boundary and can continue across pages, producing a kernel oops on an unmapped/guard page under KFENCE, DEBUG_PAGEALLOC, or a direct-map hole, and a fatal KASAN report on hardened kernels; it is repeatable at will by an unprivileged user." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/auditfilter.c" ], "versions": [ { "version": "e92eebb0d6116f942ab25dfb1a41905aa59472a8", "lessThan": "9735a9dcc307427e7d6336c54171682f1bac9789", "status": "affected", "versionType": "git" }, { "version": "e92eebb0d6116f942ab25dfb1a41905aa59472a8", "lessThan": "4540f1d23e7f387880ce46d11b5cd3f27248bf8d", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/auditfilter.c" ], "versions": [ { "version": "6.14", "status": "affected" }, { "version": "0", "lessThan": "6.14", "status": "unaffected", "versionType": "semver" }, { "version": "6.16.6", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.17", "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": "6.14", "versionEndExcluding": "6.16.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "6.17" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/9735a9dcc307427e7d6336c54171682f1bac9789" }, { "url": "https://git.kernel.org/stable/c/4540f1d23e7f387880ce46d11b5cd3f27248bf8d" } ], "title": "audit: fix out-of-bounds read in audit_compare_dname_path()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "cvssV3_1": { "scope": "UNCHANGED", "version": "3.1", "baseScore": 7.1, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH" } }, { "other": { "type": "ssvc", "content": { "id": "CVE-2025-39840", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2026-01-14T19:20:33.496174Z" } } } ], "problemTypes": [ { "descriptions": [ { "lang": "en", "type": "CWE", "cweId": "CWE-125", "description": "CWE-125 Out-of-bounds Read" } ] } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-01-14T19:23:12.172Z" } } ] } }