CVE-2026-89696nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref
- 7.5HighCVSS base score
- 0.75%Exploitation in 30 daysEPSS · top 44% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
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.
Timeline
ID reserved
By Linux
Published
- 38 days later
· 38 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Received | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.75% · top 44% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < 00c84f4eec715e501efc080a5670114189e42507
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < 2d9846fd1c767920fddd4bde30eb35cd2969df13
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < 977e6f006a7a3ffc4216ae6034f768f8de6fd138
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < 35f248bd40b47b229d4999581df45b97daadd977
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < 311f7d926630940650447cbd1c932b076b40a6c4
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < bf4d338dc8625d70c7f2cb0657d66851a7ac9154
- affected b9e8638e3d9ed8334f1f7071e081860aac37e83e – < c59738a00aa51b16adc1b5ceb7c80877168efb4d
- affected 5.6
- unaffected < 5.6
- unaffected 5.10.270 – ≤ 5.10.*
- unaffected 5.15.221 – ≤ 5.15.*
- unaffected 6.1.188 – ≤ 6.1.*
- unaffected 6.6.157 – ≤ 6.6.*
- unaffected 6.12.109 – ≤ 6.12.*
- unaffected 6.18.50 – ≤ 6.18.*
- unaffected 7.2.4 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References8
- https://git.kernel.org/stable/c/ffdc844e673d2bcb2af8c8c3eef8cdea59d0bf32 (opens in a new tab)
- https://git.kernel.org/stable/c/00c84f4eec715e501efc080a5670114189e42507 (opens in a new tab)
- https://git.kernel.org/stable/c/2d9846fd1c767920fddd4bde30eb35cd2969df13 (opens in a new tab)
- https://git.kernel.org/stable/c/977e6f006a7a3ffc4216ae6034f768f8de6fd138 (opens in a new tab)
- https://git.kernel.org/stable/c/35f248bd40b47b229d4999581df45b97daadd977 (opens in a new tab)
- https://git.kernel.org/stable/c/311f7d926630940650447cbd1c932b076b40a6c4 (opens in a new tab)
- https://git.kernel.org/stable/c/bf4d338dc8625d70c7f2cb0657d66851a7ac9154 (opens in a new tab)
- https://git.kernel.org/stable/c/c59738a00aa51b16adc1b5ceb7c80877168efb4d (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-76608 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2026-89696)Record last updated .