9.8

CVE-2026-89689: linux

CVSS: 9.8v3.1CriticalReceived
AliasesUBUNTU-CVE-2026-89689DEBIAN-CVE-2026-89689
Published 11-09-2026Last modified 19-10-2026
Open JSON

Vulnerability summary

CVE-2026-89689 is a critical (CVSS 9.8) vulnerability in linux. EPSS estimates a 0.61% chance of exploitation in the next 30 days, higher than 48.4% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.61%
0%100%
Low · +0.01 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 1
MGASA-2026-0506OPENSUSE-SU-2026:11805-1RHSA-2026:83207

Timeline

  1. 11-09-2026
    PublishedVulnerability first disclosed.
  2. 19-10-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.61%

Chance of exploitation in the next 30 days

Percentile

48%

Versus all other CVEs

30-day change

+0.01 pp

From 0.60% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.61%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Ubuntu120 products
  • linuxAll versions (No fix recorded)
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Debian1 product
  • linux< 7.2.6-1
Linux1 product
  • linux≥ fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7, < 72d40b103bb03f0124d3a3c8f71a30cbafaf6afa | ≥ fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7, < b449b134e7762ddf98653a4b1d3e76d2d212ea64 | ≥ fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7, < f5d22e372f4ac3eb287037a488c29691d52a6330 | 6.14

3 vendors · 122 products

References

7 links