CVE-2026-74627 in Linux
Summary
by MITRE • 08/22/2026
In the Linux kernel, the following vulnerability has been resolved:
net: devmem: prevent net-iov / page mixing
We should either have net_iov or page backed frags in a single skb, otherwise it blows up down the stack. Don't allow mixing in zerocopy_fill_skb_from_devmem().
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Analysis
by VulDB Data Team • 08/22/2026
The Linux kernel networking subsystem contains a critical logic flaw within the zero-copy memory management mechanism for network devices, specifically affecting how scatter-gather lists are constructed when utilizing device memory or direct access to user-space buffers. This vulnerability arises from an improper handling of fragment types in socket buffer structures during packet transmission preparation. The core issue lies in the function zerocopy_fill_skb_from_devmem which is responsible for populating a sk_buff with fragments derived directly from device memory without copying data into kernel space. In this process, the code fails to enforce mutual exclusivity between two distinct backing mechanisms: net_iov and standard page-backed fragments.
When these two fragment types are mixed within a single socket buffer structure, it leads to undefined behavior deep in the network stack during packet processing or transmission. The underlying assumption of many networking functions is that all fragments in an sk_buff share the same memory management semantics. Mixing device-memory backed references with traditional kernel page-backed pages violates this invariant because they require different cleanup routines and access patterns. Specifically, net_iov entries reference external buffers managed by user-space applications via zero-copy interfaces, while page-backed frags rely on standard kernel page refcounting mechanisms. Attempting to process a buffer containing both types can cause memory corruption, use-after-free conditions, or kernel panics as the stack attempts to apply incorrect deallocation logic to mismatched fragment descriptors.
This flaw represents a significant stability risk for systems relying on high-performance networking with zero-copy optimizations, such as those used in virtualization environments, containerized workloads, and high-frequency trading applications where latency reduction is critical. An attacker or misconfigured application could potentially trigger this condition by crafting specific network packets that exploit the fragment assembly logic to force a mix of these backing types. The operational impact includes denial of service through kernel crashes, which disrupts all network connectivity on the affected host. In more severe scenarios involving complex memory management interactions, there may be potential for privilege escalation if the corruption allows overwriting critical kernel data structures, although the primary immediate risk is system stability and availability.
From a classification perspective, this vulnerability aligns with CWE-602 Client-Side Enforcement of Server-Side Security as it involves improper handling of input assumptions regarding memory layout, but more accurately fits under CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer due to the mixing of incompatible data structures leading to out-of-bounds or invalid access patterns. In terms of attack vectors and techniques, this relates to ATT&CK technique T1055 Process Injection if viewed through the lens of memory manipulation, but more directly corresponds to resource exhaustion scenarios typical of denial-of-service attacks via malformed network inputs. The vulnerability highlights the complexity of maintaining invariants in low-level kernel networking code where performance optimizations often bypass standard safety checks.
Mitigation strategies primarily involve applying the upstream Linux kernel patch that enforces strict separation between net_iov and page-backed fragments within zerocopy_fill_skb_from_devmem. System administrators should ensure their kernels are updated to versions containing this fix, particularly if they utilize zero-copy networking features or high-performance packet processing frameworks like DPDK integrated with standard network stacks. For environments where immediate patching is not feasible, restricting the use of advanced zero-copy APIs and ensuring that applications strictly adhere to single-type fragment allocation can reduce exposure. Continuous monitoring for kernel oops messages related to net_dev_xmit or sk_buff management functions can help detect potential exploitation attempts in real-time before they lead to system crashes.