{"id":"CVE-2026-43106","state":"PUBLISHED","title":"cachefiles: fix incorrect dentry refcount in cachefiles_cull()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: fix incorrect dentry refcount in cachefiles_cull()\n\nThe patch mentioned below changed cachefiles_bury_object() to expect 2\nreferences to the 'rep' dentry.  Three of the callers were changed to\nuse start_removing_dentry() which takes an extra reference so in those\ncases the call gets the expected references.\n\nHowever there is another call to cachefiles_bury_object() in\ncachefiles_cull() which did not need to be changed to use\nstart_removing_dentry() and so was not properly considered.\nIt still passed the dentry with just one reference so the net result is\nthat a reference is lost.\n\nTo meet the expectations of cachefiles_bury_object(), cachefiles_cull()\nmust take an extra reference before the call.  It will be dropped by\ncachefiles_bury_object().","publishedAt":"2026-05-06T07:40:34.365Z","updatedAt":"2026-08-05T12:25:56.425Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7bb1eb45e43c4730cbc5a48b9e9295049fccdacb","status":"affected","lessThan":"6577df7dc7a7de128442b6192c7a32195c923480","versionType":"git"},{"version":"7bb1eb45e43c4730cbc5a48b9e9295049fccdacb","status":"affected","lessThan":"1635c2acdde86c4f555b627aec873c8677c421ed","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/cachefiles/namei.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"6.19.14","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/cachefiles/namei.c"]}],"references":["https://git.kernel.org/stable/c/6577df7dc7a7de128442b6192c7a32195c923480","https://git.kernel.org/stable/c/1635c2acdde86c4f555b627aec873c8677c421ed"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43106.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43106","state":"PUBLISHED","datePublished":"2026-05-06T07:40:34.365Z","dateUpdated":"2026-08-05T12:25:56.425Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:55.986Z"},"containers":{"cna":{"title":"cachefiles: fix incorrect dentry refcount in cachefiles_cull()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: fix incorrect dentry refcount in cachefiles_cull()\n\nThe patch mentioned below changed cachefiles_bury_object() to expect 2\nreferences to the 'rep' dentry.  Three of the callers were changed to\nuse start_removing_dentry() which takes an extra reference so in those\ncases the call gets the expected references.\n\nHowever there is another call to cachefiles_bury_object() in\ncachefiles_cull() which did not need to be changed to use\nstart_removing_dentry() and so was not properly considered.\nIt still passed the dentry with just one reference so the net result is\nthat a reference is lost.\n\nTo meet the expectations of cachefiles_bury_object(), cachefiles_cull()\nmust take an extra reference before the call.  It will be dropped by\ncachefiles_bury_object()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7bb1eb45e43c4730cbc5a48b9e9295049fccdacb","status":"affected","lessThan":"6577df7dc7a7de128442b6192c7a32195c923480","versionType":"git"},{"version":"7bb1eb45e43c4730cbc5a48b9e9295049fccdacb","status":"affected","lessThan":"1635c2acdde86c4f555b627aec873c8677c421ed","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/cachefiles/namei.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"6.19.14","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/cachefiles/namei.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/6577df7dc7a7de128442b6192c7a32195c923480"},{"url":"https://git.kernel.org/stable/c/1635c2acdde86c4f555b627aec873c8677c421ed"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable path is reached through local CacheFiles/cachefilesd activity and the `/dev/cachefiles` control interface, not by directly processing remote packets.\nAC:L - The refcount bug is deterministic once a cull operation reaches `cachefiles_cull()`; there is no attacker-uncontrolled race required, and cache pressure/cullable objects can be induced in a normal CacheFiles-backed deployment.\nPR:L - Directly opening `/dev/cachefiles` requires init-namespace `CAP_SYS_ADMIN`, but culling is normally performed by the privileged cachefilesd daemon in response to cache pressure. A local unprivileged user with access to a CacheFiles-backed mount can plausibly create cache pressure and cullable objects that cause the daemon to trigger the vulnerable command.\nUI:N - No victim user action is required once the attacker can generate the local cache activity; cachefilesd culling is daemon-driven.\nS:U - The vulnerability corrupts kernel/VFS state within the same operating-system security authority and does not cross a VM, IOMMU, or similar boundary.\nC:H - The missing extra dentry reference can produce a use-after-free/double-put on a kernel dentry. Under the required kernel guidance, UAF memory corruption is scored as capable of high confidentiality impact.\nI:H - The freed dentry can be reused while still dereferenced or put again, making this kernel memory corruption. Under the required guidance, UAFs are treated as potentially enabling arbitrary write/control-flow impact.\nA:H - The dentry refcount loss can lead to use-after-free, refcount underflow, or invalid dput paths in the kernel. Such corruption can reliably crash or oops the kernel, so availability impact is high."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:25:56.425Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"6.19.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}