CVE-2026-64132 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
ipv6: ioam: refresh hdr pointer before ioam6_event()
Reported by Sashiko:
In ipv6_hop_ioam(), the hdr pointer is initialized to point into the skb's linear data buffer. Later, the code calls skb_ensure_writable(), which might reallocate the buffer:
if (skb_ensure_writable(skb, optoff + 2 + hdr->opt_len)) goto drop;
/* Trace pointer may have changed */ trace = (struct ioam6_trace_hdr *)(skb_network_header(skb) + optoff + sizeof(*hdr));
ioam6_fill_trace_data(skb, ns, trace, true);
ioam6_event(IOAM6_EVENT_TRACE, dev_net(skb->dev), GFP_ATOMIC, (void *)trace, hdr->opt_len - 2);
If the skb is cloned or lacks sufficient linear headroom, skb_ensure_writable() will invoke pskb_expand_head(), which reallocates the skb's data buffer and frees the old one, invalidating pointers to it. While the code recalculates the trace pointer immediately after the call to skb_ensure_writable(), it fails to recalculate the hdr pointer.
This patch fixes the above by recalculating the hdr pointer before passing hdr->opt_len to ioam6_event(), so that we avoid any UaF.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability described represents a critical use-after-free condition in the Linux kernel's IPv6 implementation, specifically within the IOAM (In-situ OAM) functionality. This flaw exists in the ipv6_hop_ioam() function where improper pointer management leads to potential memory corruption and exploitation opportunities. The issue stems from the kernel's handling of socket buffer (skb) data structures during network packet processing, particularly when dealing with IPv6 options and IOAM headers.
The technical root cause involves a classic pointer invalidation scenario that occurs during buffer reallocation. When the kernel processes IPv6 packets containing IOAM options, it initializes a hdr pointer to reference data within the skb's linear data buffer. Subsequently, the code invokes skb_ensure_writable() to ensure sufficient space for modifications, which triggers buffer reallocation when the current buffer lacks adequate headroom or when the skb is cloned. This reallocation process invalidates all existing pointers to the old buffer memory location while the new buffer gets allocated at a different memory address. The kernel correctly recalculates the trace pointer after this reallocation but fails to update the hdr pointer, creating a situation where hdr pointer references freed memory.
This vulnerability falls under CWE-416 Use After Free, representing a fundamental memory safety issue that can be exploited by remote attackers to execute arbitrary code or cause system crashes. The flaw manifests during IOAM event processing when ioam6_event() is called with an invalid hdr pointer, potentially leading to information disclosure, privilege escalation, or denial of service conditions. The attack vector involves sending specially crafted IPv6 packets containing IOAM options that trigger the vulnerable code path during packet processing.
The operational impact of this vulnerability extends beyond simple system instability, as it represents a potential security risk that could be exploited in network-based attacks. Attackers could leverage this flaw to cause kernel memory corruption through carefully constructed IPv6 packets, potentially leading to privilege escalation or system compromise. The vulnerability affects systems running Linux kernels with IPv6 IOAM support and is particularly concerning given the widespread use of IPv6 networking in modern infrastructure.
Mitigation strategies should focus on applying the upstream patch that properly recalculates the hdr pointer before the ioam6_event() call, ensuring all pointers remain valid after potential buffer reallocation. System administrators should prioritize kernel updates to address this vulnerability, as the patch directly resolves the pointer invalidation issue by maintaining proper reference tracking throughout the buffer management operations. Additionally, network monitoring solutions should be configured to detect and alert on unusual IPv6 packet patterns that might indicate exploitation attempts targeting this specific vulnerability.