High [CVE-2026-64132] refresh hdr pointer before ioam6_event
This high-severity Red Hat Linux advisory covers CVE-2026-64132 affecting Red Hat Enterprise Linux 10, Shadow Migration Toolkit for Virtualization for RHEL 10, Red Hat package: kernel.
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Summary
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.
A flaw was found in the Linux kernel's IPv6 In-situ Operations, Administration, and Maintenance (IOAM) component. This vulnerability, a use-after-free, occurs when the kernel fails to correctly update a pointer after reallocating a network packet's buffer.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
- kernel-0:6.12.0-211.63.1.el10_2
- RHSA-2026:76738
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Mitigation checklist
- Ensure IPv6 In-situ Operations, Administration, and Maintenance (IOAM) processing is disabled across all network interfaces. By default, IOAM processing is disabled (value set to 0). If it has been enabled, disable it dynamically using sysctl: # sysctl -w net.ipv6.conf.all.ioam6_enabled=0 # sysctl -w net.ipv6.conf.default.ioam6_enabled=0 To persist these settings across system reboots, create a file in /etc/sysctl.d/: # cat << 'EOF' > /etc/sysctl.d/99-disable-ioam.conf net.ipv6.conf.all.ioam6_enabled = 0 net.ipv6.conf.default.ioam6_enabled = 0 EOF # sysctl --system Caveats: Disabling IOAM prevents the kernel from processing IPv6 IOAM trace options, which will impact network telemetry or diagnostic utilities relying on in-situ telemetry data. Warning: Runtime sysctl modifications take effect immediately without requiring a system restart; however, verify that interface-specific sysctl entries (net.ipv6.conf.<interface>.ioam6_enabled) are also set to 0 if previously configured.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
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