Bug 2502619 (CVE-2026-64132)

Summary: CVE-2026-64132 kernel: ipv6: ioam: refresh hdr pointer before ioam6_event()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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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. This oversight could allow an attacker to trigger a system crash, leading to a denial of service, or potentially lead to more severe impacts like information disclosure or arbitrary code execution.
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Description OSIDB Bzimport 2026-07-19 17:09:14 UTC 
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.
Comment 1 TEJ RATHI 2026-07-20 06:12:43 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071927-CVE-2026-64132-dd76@gregkh/T
Comment 3 Jon Orris 2026-10-07 20:29:10 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:76738 https://access.redhat.com/errata/RHSA-2026:76738