{"id":21618,"date":"2026-09-12T04:31:25","date_gmt":"2026-09-11T20:31:25","guid":{"rendered":"https:\/\/www.54iter.cn\/?vuln=cve-2026-89696"},"modified":"2026-09-12T04:31:25","modified_gmt":"2026-09-11T20:31:25","slug":"cve-2026-89696","status":"publish","type":"vuln","link":"https:\/\/www.54iter.cn\/?vuln=cve-2026-89696","title":{"rendered":"CVE-2026-89696 &#8211; In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: block non-SAVEF"},"content":{"rendered":"<p>In the Linux kernel, the following vulnerability has been resolved:<\/p>\n<p>nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref<\/p>\n<p>When CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can return<br \/>\nsuccess with fh_dentry and fh_export both NULL if fh_verify() returns<br \/>\nnfserr_stale and putfh-&gt;no_verify is true. The NFSD4_FH_FOREIGN flag<br \/>\nis set, but the compound dispatch loop only uses this flag to bypass<br \/>\nthe nfserr_nofilehandle check &#8212; it does not prevent subsequent ops<br \/>\nfrom running with a NULL fh_dentry.<\/p>\n<p>A remote client can exploit this by crafting a COMPOUND that includes<br \/>\nan inter-SSC COPY (which causes check_if_stalefh_allowed() to set<br \/>\nno_verify=true on the saved PUTFH) with an additional op inserted<br \/>\nbetween the source PUTFH and SAVEFH. For example, SETATTR calls<br \/>\nfh_want_write() which dereferences fh_export-&gt;ex_path.mnt without<br \/>\ncalling fh_verify() first, causing a NULL pointer dereference in the<br \/>\nnfsd kthread.<\/p>\n<p>Fix this by gating the dispatch loop: when NFSD4_FH_FOREIGN is set<br \/>\nand fh_dentry is NULL, only OP_SAVEFH (needed for the inter-SSC flow)<br \/>\nand ops with ALLOWED_WITHOUT_FH (which don&#8217;t need a resolved<br \/>\nfilehandle) may proceed. All other ops receive nfserr_stale, per<br \/>\nRFC 7862 Section 15.2.3 which specifies that foreign filehandle<br \/>\nvalidation is deferred to the consuming operation and NFS4ERR_STALE<br \/>\nreturned at that point.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In the Linux kernel, the following vulnerability has been resolved:<\/p>\n<p>nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref<\/p>\n<p>When CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-21618","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/21618","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21618"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21618"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21618"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}