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NVD / CVE Program· CNA Linux

CVE-2026-89689: nfsd: don't free session slots that are still in use

Noroxi assessment

Priority: Monitor (action score 39/100)

  • 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: 0.61% (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 72d40b103bb03f0124d3a3c8f71a30cbafaf6afa, b449b134e7762ddf98653a4b1d3e76d2d212ea64, f5d22e372f4ac3eb287037a488c29691d52a6330.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 72d40b103bb03f0124d3a3c8f71a30cbafaf6afa, b449b134e7762ddf98653a4b1d3e76d2d212ea64, f5d22e372f4ac3eb287037a488c29691d52a6330 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: don't free session slots that are still in use nfsd4_sequence() can free the very slot it is currently processing. When the session shrinker has reduced se_target_maxslots below se_fchannel.maxreqs, the shrink path checks three conditions before calling free_session_slots(): 1. se_target_maxslots < maxreqs (shrink was advertised) 2. slot->sl_generation == se_slot_gen (slot is up-to-date) 3. seq->maxslots <= se_target_maxslots (client acknowledges) However, seq->slotid is never checked against se_target_maxslots. A client using a slot in the range [se_target_maxslots, maxreqs) can satisfy all three conditions: its slot has the current generation (set by a prior SEQUENCE), and it sends sa_highest_slotid <= se_target_maxslots to acknowledge the reduction. free_session_slots() then kfrees every slot at index >= se_target_maxslots, including the caller's own slot. The function continues to write sl_seqid, sl_flags, sl_generation, and stores the dangling pointer in cstate->slot. Later, nfsd4_store_cache_entry() copies up to maxresp_cached bytes of the compound reply into the freed sl_data[] array, corrupting whatever slab object now occupies that address. Additionally, a concurrent thread processing SEQUENCE on a different high-numbered slot can have its slot freed out from under it. NFSD4_SLOT_INUSE is set under nn->client_lock before the lock is released, so any concurrent thread past SEQUENCE will have its slot marked. However, free_session_slots() does not check NFSD4_SLOT_INUSE before freeing. Fix both problems by: 1. Checking that the current request's slotid is below the shrink boundary. 2. Scanning slots in the to-be-freed range for NFSD4_SLOT_INUSE and deferring the shrink if any are active.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Sep 11, 2026
Updated
Oct 19, 2026
EPSS
0.6% · 49th percentile
CWE
—

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.6%

CNA vs NVD score

NVD
—
CNA · Linux
9.8
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.

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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.

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Affected 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

    • 6.14affected
    • fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7 and later · before 72d40b103bb03f0124d3a3c8f71a30cbafaf6afaaffected · git
    • fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7 and later · before b449b134e7762ddf98653a4b1d3e76d2d212ea64affected · git
    • fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7 and later · before f5d22e372f4ac3eb287037a488c29691d52a6330affected · git
    • before 6.14not affected · semver
    • 6.18.50 and later · up to and including 6.18.*not 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.

EcosystemPackageAffected rangeFix
AlmaLinux:10kernelbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64kbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debugbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-modulesbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-extrabefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-modulesbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-modules-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-64k-modules-extrabefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.66.1.el10_26.12.0-211.66.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-89687Sep 11, 2026 · nfsd: ensure nfsd_file_do_acquire() does not use a non-opened file
    30Monitor
  • ← EarlierCVE-2026-89688Sep 11, 2026 · nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
    39Monitor
  • Later →CVE-2026-89690Sep 11, 2026 · nfsd: defer vfree of compound ops to fix rpc_status UAF
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux72d40b103bb03f0124d3a3c8f71a30cbafaf6afaVendor (CNA)
Linux Linuxb449b134e7762ddf98653a4b1d3e76d2d212ea64Vendor (CNA)
Linux Linuxf5d22e372f4ac3eb287037a488c29691d52a6330Vendor (CNA)
almalinux:kernel6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-core6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-core6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-devel6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-modules6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-modules-core6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-devel6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-devel-matched6.12.0-211.66.1.el10_2 · AlmaLinux:10Package registry (OSV)
debian:linux7.2.6-1 · Debian:14Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel-matched0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debuginfo0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-devel0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-devel-matched0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-debuginfo0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-devel0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debug-devel-matched0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debuginfo0:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-debuginfo-common-aarch640:6.12.0-211.66.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-modules-internal0:6.12.0-211.66.1.el10_2 · Red Hat:shadow_migration_toolkit:10::el10Package registry (OSV)
rocky linux:kernel0:6.12.0-211.66.1.el10_2 · Rocky Linux:10Package 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.

EPSS, last 120 days

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 researchers

Finders, 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.

All national notices →

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
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records