CVE-2026-98038: bpf: Keep refcount_acquire nullable for borrowed RCU kptrs
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 85074498228a2500ea8b8039c49cc1ab8ad5328f, 85bfc8b6db43502444c428eaa2de20bdd2fb9064, 8d19e2cdfba9ba8c8eb6a459cd666bec00a1d2c6.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to Linux Linux 85074498228a2500ea8b8039c49cc1ab8ad5328f, 85bfc8b6db43502444c428eaa2de20bdd2fb9064, 8d19e2cdfba9ba8c8eb6a459cd666bec00a1d2c6 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: bpf: Keep refcount_acquire nullable for borrowed RCU kptrs bpf_refcount_acquire() is fallible for a borrowed reference because the object may have reached a zero refcount. The verifier therefore keeps KF_RET_NULL on the return value unless the argument is an owning reference. An RCU-protected load of a local kptr is marked MEM_ALLOC, but it only receives NON_OWN_REF when the pointee contains a graph node. A refcounted object without a graph node consequently looks like an owning reference even though the loaded register has no acquired reference state. If the program drops the last real reference while remaining in the RCU critical section, refcount_inc_not_zero() returns NULL while the verifier treats the result as non-NULL. Only classify the argument as owning when it is backed by a verifier-tracked reference. This retains the non-NULL return for pointers from bpf_obj_new(), bpf_kptr_xchg(), or an earlier successful acquisition, while requiring a NULL check for borrowed RCU kptrs. [ kkd: Rewrote commit log ]
- Published
- Sep 25, 2026
- Updated
- Oct 21, 2026
- EPSS
- 0.2% · 11th percentile
- CWE
- —
Report tools
Action score
0
Monitor
Low priority for now.
- CVSS
- 0 / 40 · —
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
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
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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.
We use this product, ask for helpAffected 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.
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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
- 6.8affected
- 1b12171533a9bb23cf6fba7262b479028b65e1e8 and later · before 85bfc8b6db43502444c428eaa2de20bdd2fb9064affected · git
- 1b12171533a9bb23cf6fba7262b479028b65e1e8 and later · before 8d19e2cdfba9ba8c8eb6a459cd666bec00a1d2c6affected · git
- 1b12171533a9bb23cf6fba7262b479028b65e1e8 and later · before 85074498228a2500ea8b8039c49cc1ab8ad5328faffected · git
- 1b12171533a9bb23cf6fba7262b479028b65e1e8 and later · before dc36739e5cc9f60485418a910b42bc95339218d2affected · git
- before 6.8not affected · semver
- 6.12.114 and later · up to and including 6.12.*not affected · semver
- 6.18.57 and later · up to and including 6.18.*not affected · semver
- 7.2.7 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.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:13 | linux | before 6.12.115-2 | 6.12.115-2 |
| Debian:14 | linux | before 7.2.7-1 | 7.2.7-1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation40Plan
- CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment40Plan
- CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()40Plan
Published before and after this one in the same product
- ← EarlierCVE-2026-98036Sep 25, 2026 · bpf: Preserve special fields in recycled rhtab elements0Monitor
- ← EarlierCVE-2026-98037Sep 25, 2026 · bpf: Reject untrusted allocated-object pointers0Monitor
- Later →CVE-2026-98039Sep 25, 2026 · bpf: Require MEM_PERCPU for percpu kptr stores0Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 85074498228a2500ea8b8039c49cc1ab8ad5328f | Vendor (CNA) |
| Linux Linux | 85bfc8b6db43502444c428eaa2de20bdd2fb9064 | Vendor (CNA) |
| Linux Linux | 8d19e2cdfba9ba8c8eb6a459cd666bec00a1d2c6 | Vendor (CNA) |
| Linux Linux | dc36739e5cc9f60485418a910b42bc95339218d2 | Vendor (CNA) |
| debian:linux | 6.12.115-2 · Debian:13 | Package registry (OSV) |
| debian:linux | 7.2.7-1 · Debian:14 | Package 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.
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 researchersFinders, 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.
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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.
- TR-26-1184 · Sep 28, 2026(Linux Kernel Güvenlik Bildirimi)
Technical details
No CVSS vector for this record, so attack conditions can't be derived.
Weakness class (CWE)
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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
- Fix✗ → ✓
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References
Show all references (3 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.