CVE-2026-64113 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
ixgbevf: fix use-after-free in VEPA multicast source pruning
ixgbevf_clean_rx_irq() prunes frames whose source MAC matches the VF's own address (VEPA multicast workaround) by freeing the skb and continuing to the next descriptor:
dev_kfree_skb_irq(skb); continue;
The skb pointer is declared outside the while loop and persists across iterations. Because the continue skips the "skb = NULL" reset at the bottom of the loop, the next iteration enters the "else if (skb)" path and calls ixgbevf_add_rx_frag() on the freed skb, dereferencing skb_shinfo(skb)->nr_frags - a use-after-free in NAPI softirq context.
The sibling driver iavf already handles this correctly by nulling the pointer before continuing. Apply the same pattern here.
I do not have ixgbevf hardware; the bug was found by static analysis (scan_drop_continue_loops.py + semgrep drop_continue_in_loop, multi-tool corroboration with the highest score in the scan). The UAF was confirmed under KASAN by loading a test module that reproduces the exact code pattern (alloc skb, kfree_skb, then read skb_shinfo(skb)->nr_frags):
BUG: KASAN: slab-use-after-free in ixgbevf_uaf_test_init+0x100/0x1000 Read of size 8 at addr 000000006163ae78 by task insmod/30 freed 208-byte region [000000006163adc0, 000000006163ae90)
QEMU emulates igb (82576) but not ixgbe (82599), and the igbvf VF driver does not include the VEPA source pruning path, so a full end-to-end reproduction with emulated hardware was not possible.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability under analysis involves a use-after-free condition in the ixgbevf network driver within the Linux kernel, specifically affecting virtual function implementations of Intel's 82599 series adapters. This flaw manifests during packet processing in the ixgbevf_clean_rx_irq() function where multicast frames with source MAC addresses matching the VF's own address are pruned using a VEPA (Virtual Ethernet Port Aggregator) multicast workaround. The implementation pattern demonstrates a classic software defect where memory management practices fail to account for control flow paths that skip critical pointer reset operations.
The technical root cause stems from improper handling of the skb (socket buffer) pointer lifecycle within a while loop structure. When a frame is identified for pruning, the code executes dev_kfree_skb_irq(skb) followed immediately by continue; which bypasses the normal loop termination logic that would reset skb = NULL. This critical oversight allows subsequent loop iterations to proceed with an already freed pointer, creating a dangerous scenario where the same memory location gets accessed after deallocation. The vulnerability occurs in NAPI (Network API) softirq context, making it particularly concerning as it can lead to kernel crashes or potential privilege escalation.
The operational impact of this use-after-free vulnerability extends beyond simple system instability, representing a significant security risk that could be exploited in containerized environments or virtualized systems where network drivers are frequently accessed. The flaw affects the ixgbevf driver specifically and aligns with CWE-416, which categorizes use-after-free conditions as critical memory safety issues. The vulnerability demonstrates how seemingly minor code paths can create substantial security implications when proper resource management is not maintained across all execution branches. According to ATT&CK framework, this represents a potential privilege escalation vector through kernel memory corruption techniques.
The fix for this vulnerability follows established best practices demonstrated by the sibling driver iavf which correctly implements pointer nullification before continue statements. This defensive programming approach ensures that freed pointers cannot be accidentally dereferenced in subsequent iterations, preventing the use-after-free condition from occurring. The remediation strategy involves modifying the loop structure to reset skb = NULL immediately after calling dev_kfree_skb_irq(skb) before executing continue; as shown in the referenced patch. The bug was identified through static analysis tools including scan_drop_continue_loops.py and semgrep drop_continue_in_loop rules, with confirmation achieved via KASAN (Kernel Address Sanitizer) testing that reproduced the exact memory access pattern leading to the slab-use-after-free error.
The absence of actual ixgbevf hardware during discovery limited full end-to-end validation, but the static analysis approach provided sufficient confidence in the vulnerability's existence and exploitability. The test module verification confirmed the precise conditions that trigger the use-after-free through direct memory access patterns that mirror the original code path. While QEMU emulates igb hardware for testing purposes, it does not support ixgbe hardware emulation, preventing comprehensive hardware-level validation, yet the software-only reproduction validates the fundamental flaw exists in the driver's logic. This vulnerability highlights the importance of thorough code review practices and demonstrates how automated static analysis tools can identify subtle but critical memory safety issues that might otherwise remain undetected in manual code reviews or traditional testing approaches.