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NVD / CVE Program· CNA Linux

CVE-2026-99233: tracing/histograms: Verify event_call identity when updating synth_event refcount

Noroxi assessment

Priority: Monitor (action score 31/100)

  • 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: 0.12% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 06e816bed499fe47f39f12044382cc5d064485fb, 23b4106e8b35823acc79e206c7745f55b9cfd78b, 3403d9bb27ebc3572bd048620746b4414e073bf9.

Low priority for now. Upgrade to Linux Linux 06e816bed499fe47f39f12044382cc5d064485fb, 23b4106e8b35823acc79e206c7745f55b9cfd78b, 3403d9bb27ebc3572bd048620746b4414e073bf9 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: tracing/histograms: Verify event_call identity when updating synth_event refcount In event_hist_trigger_parse() and hist_unreg_all(), the histogram registration and unregistration paths look up find_synth_event() using trace_event_name(file->event_call) and adjust se->ref if a match is found. Because find_synth_event() only compares the event basename, registering or removing a histogram on a non-synthetic trace event whose basename matches a synthetic event erroneously modifies the synthetic event's reference count. If a histogram is registered on the non-synthetic event before the synthetic event is created and removed afterwards, se->ref is decremented without a matching increment, allowing the synthetic event to be freed while an active histogram action still holds a pointer to it. Introduce find_synth_event_call() to verify that &se->call matches file->event_call before adjusting se->ref.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Nov 2, 2026
Updated
Nov 3, 2026
EPSS
0.1% · 1th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · Linux
7.8
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.

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.

Follow CVE-2026-99233

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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

    • 4.17affected
    • 4b147936fa509650beaf638b331573c23ba4d609 and later · before 381f543ed35c434d5b707369aa5dcd69ecf440afaffected · git
    • 4b147936fa509650beaf638b331573c23ba4d609 and later · before 4472579bd1c83708b6fe623c870cdf728e947205affected · git
    • 4b147936fa509650beaf638b331573c23ba4d609 and later · before 23b4106e8b35823acc79e206c7745f55b9cfd78baffected · git
    • 4b147936fa509650beaf638b331573c23ba4d609 and later · before 06e816bed499fe47f39f12044382cc5d064485fbaffected · git
    • 4b147936fa509650beaf638b331573c23ba4d609 and later · before 5597bb8db6855fcb97a67196d227fea359bcd81caffected · git
    • 4b147936fa509650beaf638b331573c23ba4d609 and later · before cf4e31d5da80fae4c9cdbe7af55b7c3ad213f0e4affected · git
    • 4b147936fa509650beaf638b331573c23ba4d609 and later · before 3403d9bb27ebc3572bd048620746b4414e073bf9affected · git
    • before 4.17not affected · semver
    • 6.1.191 and later · up to and including 6.1.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-16.12.115-1

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-2026-99231Nov 2, 2026 · io_uring/waitid: own the request before clearing ->head
    31Monitor
  • ← EarlierCVE-2026-99232Nov 2, 2026 · tracing/syscalls: Use copy_from_user for the faultable syscall buffer
    0Monitor
  • Later →CVE-2026-99234Nov 2, 2026 · tracing: Unregister field variable histograms when the command fails
    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 Linux06e816bed499fe47f39f12044382cc5d064485fbVendor (CNA)
Linux Linux23b4106e8b35823acc79e206c7745f55b9cfd78bVendor (CNA)
Linux Linux3403d9bb27ebc3572bd048620746b4414e073bf9Vendor (CNA)
Linux Linux381f543ed35c434d5b707369aa5dcd69ecf440afVendor (CNA)
Linux Linux4472579bd1c83708b6fe623c870cdf728e947205Vendor (CNA)
Linux Linux5597bb8db6855fcb97a67196d227fea359bcd81cVendor (CNA)
Linux Linuxcf4e31d5da80fae4c9cdbe7af55b7c3ad213f0e4Vendor (CNA)
debian:linux6.12.115-1 · Debian:13Package 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.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 5, 2026+2 d
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).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • 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
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/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✗ → ✓
  2. Exploit maturity— → none

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

References

Show all references (6 more)

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

All records