{"id":"CVE-2026-89695","summary":"nfsd: cap decoded POSIX ACL count to bound sort cost","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: cap decoded POSIX ACL count to bound sort cost\n\nnfsd4_decode_posixacl() reads a u32 entry count off the wire and passes\nit straight to posix_acl_alloc() and sort_pacl_range(). The latter is\nan O(n^2) bubble sort, so a client-chosen count drives unbounded CPU in\nthe server's compound processing path.\n\n    nfsd4_decode_posixacl()\n      xdr_stream_decode_u32(&count)       /* uncapped u32 */\n      posix_acl_alloc(count, GFP_KERNEL)\n      sort_pacl_range(*acl, 0, count - 1) /* O(n^2) bubble sort */\n\nThe encoder side in the same file already rejects ACLs whose a_count\nexceeds NFS_ACL_MAX_ENTRIES, but the decoder introduced in commit\n5fc51dfc2eb1 (\"NFSD: Add support for XDR decoding POSIX draft ACLs\")\nomitted the symmetric check.\n\nFix by rejecting a wire count greater than NFS_ACL_MAX_ENTRIES with\nnfserr_inval, before any allocation, so the sort is bounded by\nNFS_ACL_MAX_ENTRIES^2 comparisons.\n\nWhile we're in here, also fix the nfserr_resource return if\nposix_acl_alloc() fails. That's not a legal error code for v4.1+. Change\nit to return nfserr_jukebox as that's more appropriate for memory\nallocation failures.","modified":"2026-09-13T03:47:20.171719495Z","published":"2026-09-11T19:46:14.258Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89695.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/4bc1108e876153a2dd6d874052b99182c3603135"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ea14d71d6ecb925673761bcf79f781f7dc9042cc"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89695.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89695"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05"},{"fixed":"ea14d71d6ecb925673761bcf79f781f7dc9042cc"},{"fixed":"4bc1108e876153a2dd6d874052b99182c3603135"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89695.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.0.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89695.json"}}],"schema_version":"1.9.0"}