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no cvss —

CVE-2026-98038 json

bpf: Keep refcount_acquire nullable for borrowed RCU kptrs

published last mo. modified 21d ago also EUVD-2026-86691

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

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 ]

Patch / fix

  • Linux Linux 6.12.114, 6.18.57, 7.2.7, 7.3
  • linux Debian 13 6.12.115-2
  • linux Debian 14 7.2.7-1

debian advisories DEBIAN-CVE-2026-98038

  • linux Ubuntu 26.04 LTS 7.0.0-43.43
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1017.18
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1017.19
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1010.11
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1018.18
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1020.21
  • linux-oracle Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-aws-7.0 Ubuntu 24.04 LTS 7.0.0-1017.18~24.04.1

ubuntu advisories UBUNTU-CVE-2026-98038

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source openSUSE Tumbleweed 7.2.9-1.1

opensuse advisories openSUSE-SU-2026:12074-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-98038 updated cvss 5.5

kernel: bpf: Keep refcount_acquire nullable for borrowed RCU kptrs

  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more Red Hat Enterprise Linux 10 kernel Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-selftests-internal Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-11).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

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