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NVD / CVE Program· CNA Linux

CVE-2026-97922: tracing: Free histogram var refs regardless of how often they are referenced

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 4.20, 4bddcb346a6cf4615ca77f69a589623b877ca267, 4cff53bb19412c6f2d90b50678de5c3903f7f96a; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.158.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 4.20, 4bddcb346a6cf4615ca77f69a589623b877ca267, 4cff53bb19412c6f2d90b50678de5c3903f7f96a; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.158.1-1 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: tracing: Free histogram var refs regardless of how often they are referenced Using the same variable three or more times in one hist trigger leaks the variable reference and its strings when the trigger is removed. commit 656fe2ba85e8 ("tracing: Use hist trigger's var_ref array to destroy var_refs") made a trigger's var_refs[] array the only owner of a var ref: destroy_hist_field() returns early for HIST_FIELD_FL_VAR_REF, so the field expressions never destroy one. One entry, freed once, no count needed. commit 8bcebc77e85f ("tracing: Fix histogram code when expression has same var as value") then made repeated references share one object and added a count of them. Only the increment side exists, since those expressions still return early and never drop a reference, so __destroy_hist_field() sees how many references were created rather than how many are left. It frees when the decremented count is 0 or 1, so two references work and three or more leak. Sharing kept one array entry per object, and create_var_ref() searches and appends within a single trigger, so nothing outside it holds the object. Removing a trigger whose variables are still referenced is already refused by check_var_refs() with -EBUSY. Drop the count and free unconditionally.

—No exploit Fix available
Published
Sep 25, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 11th 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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Noroxi analysis

What does it mean in your environment?

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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

    • ce28d664054df01997baace61d1defca77689798, bf470f051556b610265ea02ad2102de75e8e619c, 5.5affected
    • 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 and later · before a1f1d64a0a9791c842c4646253daf6ac0313eac7affected · git
    • 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 and later · before b513a4c60a7aa1f4b4c2a48544ab003cb36f1e94affected · git
    • 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 and later · before e7b6d67b43caee9183a4374d23641578ea556e6caffected · git
    • 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 and later · before 4cff53bb19412c6f2d90b50678de5c3903f7f96aaffected · git
    • 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 and later · before 94bbd65da4ae26592fa1977a74ee94218ab02a26affected · git
    • 8bcebc77e85f3d7536f96845a0fe94b1dddb6af0 and later · before 4bddcb346a6cf4615ca77f69a589623b877ca267affected · git
    • 4.19.100 and later · before 4.20affected · semver
    • 5.4.16 and later · before 5.5affected · semver
    • before 5.5not 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 7.2.7-17.2.7-1

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-2026-97920Sep 25, 2026 · tracing: Keep the entry count when the histogram stats allocation fails
    0Monitor
  • ← EarlierCVE-2026-97921Sep 25, 2026 · tracing: Free histogram the field rejected for a bad modifier
    0Monitor
  • Later →CVE-2026-97923Sep 25, 2026 · tracing: Free histogram the var ref when its initialization 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 Linux4.20Vendor (CNA)
Linux Linux4bddcb346a6cf4615ca77f69a589623b877ca267Vendor (CNA)
Linux Linux4cff53bb19412c6f2d90b50678de5c3903f7f96aVendor (CNA)
Linux Linux5.5Vendor (CNA)
Linux Linux94bbd65da4ae26592fa1977a74ee94218ab02a26Vendor (CNA)
Linux Linuxa1f1d64a0a9791c842c4646253daf6ac0313eac7Vendor (CNA)
Linux Linuxb513a4c60a7aa1f4b4c2a48544ab003cb36f1e94Vendor (CNA)
Linux Linuxe7b6d67b43caee9183a4374d23641578ea556e6cVendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.06.6.158.1-1 · 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✗ → ✓

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References

Show all references (5 more)

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

All records