CVE-2026-89695: nfsd: cap decoded POSIX ACL count to bound sort cost
Noroxi assessment
Priority: Monitor (action score 30/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.48% (FIRST EPSS).
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: Linux Linux 4bc1108e876153a2dd6d874052b99182c3603135, ea14d71d6ecb925673761bcf79f781f7dc9042cc.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to Linux Linux 4bc1108e876153a2dd6d874052b99182c3603135, ea14d71d6ecb925673761bcf79f781f7dc9042cc or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
In the Linux kernel, the following vulnerability has been resolved: nfsd: cap decoded POSIX ACL count to bound sort cost nfsd4_decode_posixacl() reads a u32 entry count off the wire and passes it straight to posix_acl_alloc() and sort_pacl_range(). The latter is an O(n^2) bubble sort, so a client-chosen count drives unbounded CPU in the server's compound processing path. nfsd4_decode_posixacl() xdr_stream_decode_u32(&count) /* uncapped u32 */ posix_acl_alloc(count, GFP_KERNEL) sort_pacl_range(*acl, 0, count - 1) /* O(n^2) bubble sort */ The encoder side in the same file already rejects ACLs whose a_count exceeds NFS_ACL_MAX_ENTRIES, but the decoder introduced in commit 5fc51dfc2eb1 ("NFSD: Add support for XDR decoding POSIX draft ACLs") omitted the symmetric check. Fix by rejecting a wire count greater than NFS_ACL_MAX_ENTRIES with nfserr_inval, before any allocation, so the sort is bounded by NFS_ACL_MAX_ENTRIES^2 comparisons. While we're in here, also fix the nfserr_resource return if posix_acl_alloc() fails. That's not a legal error code for v4.1+. Change it to return nfserr_jukebox as that's more appropriate for memory allocation failures.
- Published
- Sep 11, 2026
- Updated
- Oct 19, 2026
- EPSS
- 0.4% · 41th percentile
- CWE
- —
Report tools
Action score
30
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.4%
CNA vs NVD score
- NVD
- —
- CNA · Linux
- 7.5
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- 7.0affected
- 5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05 and later · before ea14d71d6ecb925673761bcf79f781f7dc9042ccaffected · git
- 5fc51dfc2eb160bd7ab3251ab1767cacf9c8bf05 and later · before 4bc1108e876153a2dd6d874052b99182c3603135affected · git
- before 7.0not affected · semver
- 7.2.4 and later · up to and including 7.2.*not affected · semver
- 7.3 and laternot affected · original_commit_for_fix
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:14 | linux | before 7.2.6-1 | 7.2.6-1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation40Plan
- CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment40Plan
- CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()40Plan
Published before and after this one in the same product
- ← EarlierCVE-2026-89693Sep 11, 2026 · nfsd: check nfsd4_acl_to_attr() return value in nfsd4_create()0Monitor
- ← EarlierCVE-2026-89694Sep 11, 2026 · nfsd: check client ownership when cancelling a copy-notify stateid0Monitor
- Later →CVE-2026-89696Sep 11, 2026 · nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref30Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 4bc1108e876153a2dd6d874052b99182c3603135 | Vendor (CNA) |
| Linux Linux | ea14d71d6ecb925673761bcf79f781f7dc9042cc | Vendor (CNA) |
| debian:linux | 7.2.6-1 · Debian:14 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-26-1085 · Sep 14, 2026(Linux Kernel Güvenlik Bildirimi)
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
—
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (1 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.