EUVD-2026-39310
GHSA-gv3c-2ghh-53g2
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Local netfilter ioctl leaks one kernel virtual address yielding C:L; no crash or integrity change occurs, so A:N and I:N are correct.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
netfilter: x_tables: avoid leaking percpu counter pointers
The native and compat get-entries paths copy the fixed rule entry header from the kernelized rule blob to userspace before overwriting the entry's counter fields with a sanitized counter snapshot.
On SMP kernels, entry->counters.pcnt contains the percpu allocation address used by x_tables rule counters. A caller can provide a userspace buffer that faults during the initial fixed-header copy after pcnt has been copied but before the later sanitized counter copy runs. The syscall then returns -EFAULT while leaving the raw percpu pointer in userspace.
Copy only the fixed entry prefix before counters from the kernelized rule blob, then copy the sanitized counter snapshot into the counter field. Apply this ordering to the IPv4, IPv6, and ARP native and compat get-entries implementations so a fault cannot expose the internal percpu counter pointer.
AnalysisAI
Netfilter x_tables in the Linux kernel leaks raw percpu counter pointer addresses to userspace on SMP systems via a crafted fault-window attack against the get-entries path. A local user with netfilter access can engineer a userspace buffer that triggers a page fault after the kernel copies the internal percpu allocation pointer (pcnt) but before the sanitized counter snapshot overwrites it, causing the syscall to return -EFAULT while leaving the raw kernel virtual address exposed in the caller's buffer. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Local shell access is required - this is not remotely exploitable. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD-assigned CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, score 5.5) contains an internal inconsistency that defenders should not act on uncritically. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local user on an SMP Linux system with CAP_NET_ADMIN access (or via an unprivileged user namespace) allocates a userspace buffer using mmap, then marks the page covering the counter field offset as PROT_NONE via mprotect. The caller invokes the netfilter get-entries ioctl, the kernel copies the raw percpu pointer into the accessible head of the buffer before hitting the faulting page and returning -EFAULT; the caller reads the now-populated buffer prefix to recover the kernel virtual address. … |
| Remediation | Upgrade to the patched kernel for the active stable branch: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13, or 7.1 as confirmed by EUVD-2026-39310. … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
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