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NVD / CVE Program· CNA Linux

CVE-2026-89923: KVM: s390: Free guest debug data on vcpu destroy

Noroxi assessment

Priority: Monitor (action score 0/100)

  • 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: 0.21% (FIRST EPSS).
  • Fixed version: Linux Linux 053f2068cf9b0654b651fed5ad7649d3deb982bf, 544a5a665019cef394ce8bda97fa7a2cab253781, 6c996b12bbe4a6023076e8eee3cfaf2cc99db76c; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 053f2068cf9b0654b651fed5ad7649d3deb982bf, 544a5a665019cef394ce8bda97fa7a2cab253781, 6c996b12bbe4a6023076e8eee3cfaf2cc99db76c; azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 6.6.157.1-1 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: KVM: s390: Free guest debug data on vcpu destroy kvm_s390_clear_bp_data() is only called from kvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or disables debugging. A vCPU that is destroyed while hardware breakpoints are still armed - the normal case when the VMM just exits or crashes - leaks hw_bp_info, hw_wp_info and all old_data buffers, since generic KVM frees the vCPU right after kvm_arch_vcpu_destroy(). That is bounded by MAX_BP_COUNT entries, so roughly 8 KiB per vCPU, but it is unbounded over VM lifetimes. The allocations are GFP_KERNEL_ACCOUNT, so the charge also outlives the exiting process and pins dying memcgs. Fix by clearing the debug data on vCPU destruction. Calling it unconditionally is fine: struct kvm_vcpu is zero allocated, so for a vCPU that never enabled debugging the counters are 0 and the pointers NULL.

—No exploit Fix available
Published
Sep 16, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 10th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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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

    • 3.16affected
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before 053f2068cf9b0654b651fed5ad7649d3deb982bfaffected · git
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before 6c996b12bbe4a6023076e8eee3cfaf2cc99db76caffected · git
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before d6280fc540d8f4653c9b54a78cb747e128070f5eaffected · git
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before 544a5a665019cef394ce8bda97fa7a2cab253781affected · git
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before 9a32c4c6a6c23b7f5bf765eb5b83ba7f64a8ec63affected · git
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before b5acacfdb8966abff91836c1c5bd7da59d8a526eaffected · git
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before e4d8b7f176b976474e0800ba71ee2dfa3ce263c9affected · git
    • 27291e2165b6de70c476b7b675308113edd69a60 and later · before e7f698b09d4a7c36b299acf680fc50fe868e2bcdaffected · git
    • before 3.16not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.190-16.1.190-1
Debian:12linux-6.12before 6.12.111-1~deb12u16.12.111-1~deb12u1
Debian:13linuxbefore 6.12.111-16.12.111-1
Debian:14linuxbefore 7.2.6-17.2.6-1

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-2026-89921Sep 16, 2026 · KVM: s390: Zero initialize data structures for inject_pfault_token
    0Monitor
  • ← EarlierCVE-2026-89922Sep 16, 2026 · KVM: s390: Take srcu when importing watchpoint data
    31Monitor
  • Later →CVE-2026-89924Sep 16, 2026 · KVM: s390: Fix old_data leak in guest debug error path
    0Monitor

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 Linux053f2068cf9b0654b651fed5ad7649d3deb982bfVendor (CNA)
Linux Linux544a5a665019cef394ce8bda97fa7a2cab253781Vendor (CNA)
Linux Linux6c996b12bbe4a6023076e8eee3cfaf2cc99db76cVendor (CNA)
Linux Linux9a32c4c6a6c23b7f5bf765eb5b83ba7f64a8ec63Vendor (CNA)
Linux Linuxb5acacfdb8966abff91836c1c5bd7da59d8a526eVendor (CNA)
Linux Linuxd6280fc540d8f4653c9b54a78cb747e128070f5eVendor (CNA)
Linux Linuxe4d8b7f176b976474e0800ba71ee2dfa3ce263c9Vendor (CNA)
Linux Linuxe7f698b09d4a7c36b299acf680fc50fe868e2bcdVendor (CNA)
azl3 kernel 6.6.150.1-1 on Azure Linux 3.0—Microsoft (MSRC)
azl3 kernel 6.6.152.1-1 on Azure Linux 3.06.6.157.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.1.190-1 · Debian:12Package registry (OSV)
debian:linux6.12.111-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.111-1~deb12u1 · Debian:12Package 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

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

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 (7 more)

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

All records