High

Use-after-free in Linux kernel BPF bpf_trampoline_link_cgroup_shim

IdentifiersCVE-2026-23319CWE-416· Use After Free

CVE-2026-23319 is a local use-after-free vulnerability in the Linux kernel BPF subsystem, specifically in bpf_trampoline_link_cgroup_shim. The flaw arises from a race in shim link lifetime management: bpf_link_put can decrement the refcount of shim_link->link.link to zero, causing the object to be considered released while it may still remain reachable through tr->progs_hlist via cgroup_shim_find. Because removal from tr->progs_hlist is deferred to bpf_shim_tramp_link_release, there is a window in which another process can obtain and use a stale reference through bpf_trampoline_link_cgroup_shim, triggering a use-after-free. The upstream fix adds an atomic non-zero refcount check so the link reference is only incremented if it has not already reached zero.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can cause kernel memory-safety violations in the BPF path, leading to kernel crashes and potentially enabling compromise of confidentiality, integrity, and availability. The provided scoring context characterizes the issue as local and high impact to C, I, and A. At minimum, the bug is demonstrably exploitable for denial of service via kernel crash; depending on heap state and exploitability in a given build, it may also provide a path to more serious kernel-level impact.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure by restricting local access to systems, limiting the ability of untrusted users or workloads to exercise BPF functionality, and minimizing opportunities for concurrent local interaction with the affected BPF/cgroup trampoline path. Because the issue is a kernel race in local BPF handling, mitigation is only partial without a patched kernel.

Remediation

Patch, then assume compromise.

Apply a kernel update containing the fix for CVE-2026-23319. The remediation is the upstream change that adds an atomic non-zero check in bpf_trampoline_link_cgroup_shim and only increments the link refcount when it is not already zero. Vendor advisories in the provided context indicate fixed kernel packages were released across multiple SUSE product lines, including versions such as kernel-default 6.4.0-41.1 for SUSE Linux Micro 6.0/6.1, kernel-default 6.12.0-160000.28.1 for SLES 16.0-related products, and kernel-default 6.4.0-150700.53.37.1 for SLES 15 SP7-related products. Reboot after installing the updated kernel.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

LinuxLinux Kerneloperating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

13 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

13 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

What this page doesn’t show

The version that knows your environment.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity1