EUVD-2026-64568
GHSA-75cj-q634-phhq
Severity by source
AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Local vector; AC:H reflects requirement for VM-backed RMB multi-page splice path; PR:L for AF_SMC socket creation without root.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
net: smc: fix splice entry lifetime imbalance in smc_rx_splice
smc_rx_splice() passes pages to splice_to_pipe() before taking the references that cover the lifetime of each splice entry. In the VM-backed RMB path, splice_to_pipe() may drop unqueued entries through smc_rx_spd_release(), while queued entries are released later via the pipe buffer callback.
The old post-splice accounting also derives the number of queued VM pages from an offset mutated while building the descriptor, and a multi-page splice pairs one sock_hold() with multiple sock_put() calls.
Take the page and socket references for every candidate entry before splice_to_pipe(), and drop the matching private state, page reference, and socket reference from smc_rx_spd_release() for entries that never get queued. This fixes a refcount imbalance that can underflow page refcounts and trigger a use-after-free.
AnalysisAI
Use-after-free in the Linux kernel's SMC (Shared Memory Communications) subsystem allows a local attacker to trigger kernel memory corruption via a refcount underflow in smc_rx_splice(). The flaw arises because pages are handed to splice_to_pipe() before page and socket references are taken, so entries dropped by smc_rx_spd_release() are released without a matching reference, and multi-page splices pair one sock_hold() with multiple sock_put() calls. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local access to a Linux system with the SMC kernel module loaded or compiled in (CONFIG_SMC). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD-assigned CVSS 3.1 score of 8.4 (AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) overstates exploitability in two key dimensions. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local unprivileged user on an IBM Z or RoCE-connected system creates an AF_SMC socket and initiates a splice receive operation designed to traverse the VM-backed RMB code path with a multi-page transfer. When splice_to_pipe() drops unqueued entries before references are taken, the attacker triggers a page refcount underflow; the freed kernel page is subsequently reclaimed and reused, allowing the attacker to read or corrupt kernel memory via the dangling reference. … |
| Remediation | Upgrade to a patched stable kernel: 6.1.183, 6.6.152, 6.12.104, 6.18.45, 7.1.9, or 7.2 per the fixes documented at https://git.kernel.org/stable/c/c841789e456ec6751342fa800639ce8e82ff0e6b and the additional stable commits referenced by CVE-2026-74631. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Within 24 hours, inventory Linux systems in your environment and identify those with external user access or requiring elevated privileges. …
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