CVE-2026-89696
CVE CVE-2026-89696EUVD EUVD-2026-76608Published 2026-09-11T19:46:15.000ZLast changed 2026-09-14T12:02:03.000ZCVSS 7.5
What the advisory describes
In the Linux kernel, the following vulnerability has been resolved: nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref When CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can return success with fh_dentry and fh_export both NULL if fh_verify() returns nfserr_stale and putfh->no_verify is true. The NFSD4_FH_FOREIGN flag is set, but the compound dispatch loop only uses this flag to bypass the nfserr_nofilehandle check -- it does not prevent subsequent ops from running with a NULL fh_dentry. A remote client can exploit this by crafting a COMPOUND that includes an inter-SSC COPY (which causes check_if_stalefh_allowed() to set no_verify=true on the saved PUTFH) with an additional op inserted between the source PUTFH and SAVEFH. For example, SETATTR calls fh_want_write() which dereferences fh_export->ex_path.mnt without calling fh_verify() first, causing a NULL pointer dereference in the nfsd kthread. Fix this by gating the dispatch loop: when NFSD4_FH_FOREIGN is set and fh_dentry is NULL, only OP_SAVEFH (needed for the inter-SSC flow) and ops with ALLOWED_WITHOUT_FH (which don't need a resolved filehandle) may proceed. All other ops receive nfserr_stale, per RFC 7862 Section 15.2.3 which specifies that foreign filehandle validation is deferred to the consuming operation and NFS4ERR_STALE returned at that point.
Source: EUVD (ENISA), in the words of the advisory.
Products the advisory names
These come from the advisory itself, not from any check we performed.
- Linux — Linux patch: 5.10.270; 5.6; patch: 6.6.157; b9e8638e3d9ed8334f1f7071e081860aac37e83e <ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32; patch: 6.12.109; b9e8638e3d9ed8334f1f7071e081860aac37e83e <00c84f4eec715e501efc080a5670114189e42507; patch: 0; b9e8638e3d9ed8334f1f7071e081860aac37e83e <977e6f006a7a3ffc4216ae6034f768f8de6fd138; patch: 6.1.188; b9e8638e3d9ed8334f1f7071e081860aac37e83e <35f248bd40b47b229d4999581df45b97daadd977; b9e8638e3d9ed8334f1f7071e081860aac37e83e <c59738a00aa51b16adc1b5ceb7c80877168efb4d; b9e8638e3d9ed8334f1f7071e081860aac37e83e <311f7d926630940650447cbd1c932b076b40a6c4; b9e8638e3d9ed8334f1f7071e081860aac37e83e <bf4d338dc8625d70c7f2cb0657d66851a7ac9154; patch: 6.18.50; patch: 7.3-rc1; patch: 5.15.221; b9e8638e3d9ed8334f1f7071e081860aac37e83e <2d9846fd1c767920fddd4bde30eb35cd2969df13; patch: 7.2.4
The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.
Carried in the product catalogue
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- Linux — Linux
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