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Linux Kernel CVE-2026-53228

| EUVDEUVD-2026-39319 CRITICAL
2026-06-25 416baaa9-dc9f-4396-8d5f-8c081fb06d67 GHSA-5q2p-7748-g6qp
Information Disclosure Linux Red Hat Suse
Critical
Disputed · 9.8 Vendor: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
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Severity by source

Sources disagree (Medium–Critical)
Vendor (416baaa9-dc9f-4396-8d5f-8c081fb06d67) PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
4.8 MEDIUM

AC:H because triggering needs a GSO/cloned-skb race on a non-default SIT tunnel; C:L for a bounded freed-memory read and A:L for a possible oops; no integrity impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
SUSE
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Red Hat
7.0 MEDIUM
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

5
Analysis Generated
Jun 28, 2026 - 09:38 vuln.today
CVSS changed
Jun 28, 2026 - 08:22 NVD
9.8 (CRITICAL)
Patch available
Jun 25, 2026 - 10:32 EUVD
CVE Published
Jun 25, 2026 - 09:16 cve.org
UNKNOWN (no severity yet)
CVE Published
Jun 25, 2026 - 09:16 cve.org
CRITICAL 9.8

DescriptionCVE.org

In the Linux kernel, the following vulnerability has been resolved:

ipv6: sit: reload inner IPv6 header after GSO offloads

ipip6_tunnel_xmit() caches the inner IPv6 header pointer at function entry and continues using it after iptunnel_handle_offloads().

For GSO skbs, iptunnel_handle_offloads() calls skb_header_unclone(). When the skb header is cloned, skb_header_unclone() can call pskb_expand_head(), which may move the skb head. The pskb_expand_head() contract requires pointers into the skb header to be reloaded after the call.

If the later skb_realloc_headroom() branch is not taken, SIT uses the stale iph6 pointer to read the inner hop limit and DS field. That can read from a freed skb head after the old head's remaining clone is released.

Reload iph6 after the offload helper succeeds and before subsequent reads from the inner IPv6 header. Keep the existing reload after skb_realloc_headroom(), since that branch can also replace the skb.

AnalysisAI

Use-after-free read in the Linux kernel's IPv6 SIT (IPv6-in-IPv4) tunnel transmit path lets a stale inner-IPv6-header pointer be dereferenced after GSO offload processing relocates the skb head, exposing freed kernel memory or crashing the host. The flaw affects systems running SIT tunnels in ipip6_tunnel_xmit(), where iptunnel_handle_offloads() may call pskb_expand_head() and move the buffer while the code keeps reading the old iph6 pointer. There is no public exploit identified at time of analysis; EPSS is low (0.18%, 8th percentile) and the issue is not in CISA KEV. The vendor-tagged impact is Information Disclosure, which is materially narrower than the assigned CVSS 9.8.

Technical ContextAI

The vulnerable code is the IPv6-over-IPv4 tunnel driver (SIT, RFC 4213) in net/ipv6/sit.c. ipip6_tunnel_xmit() caches a pointer to the inner IPv6 header (iph6) at function entry, then calls iptunnel_handle_offloads() to set up Generic Segmentation Offload (GSO). For cloned skbs, that helper invokes skb_header_unclone(), which can call pskb_expand_head() and reallocate the skb head buffer. The pskb_expand_head() contract requires all pointers into the skb header to be reloaded afterward; SIT failed to do so on the path where skb_realloc_headroom() is not subsequently taken, so it read the inner hop limit and DS/traffic-class fields through a dangling pointer into a freed buffer. This is a classic use-after-free / use-of-stale-pointer-after-free condition (CWE-416 / CWE-825); the provided CWE field is N/A, so this classification is inferred from the description.

RemediationAI

Vendor-released patch: upgrade to a fixed stable kernel - 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13, or 7.1 (or your distribution's backport referencing these git.kernel.org commits, e.g. 0bfa7bba1f41 / fddd41445a05). For distro kernels, install the vendor errata kernel and reboot. If patching must be deferred, the most effective compensating control is to avoid the vulnerable code path entirely: do not configure SIT (IPv6-in-IPv4) tunnels, and where present tear them down with 'ip link set sit0 down' / remove sit tunnel interfaces, or blacklist the 'sit' module (modprobe blacklist) on hosts that do not require IPv6-over-IPv4 transition tunneling - the trade-off is loss of any legacy 6in4 connectivity that depends on it. Disabling GSO on the tunnel interface (ethtool -K) may reduce the trigger surface but is not a guaranteed fix and can degrade throughput, so it should not be relied on as a substitute for the patch.

Same technique Information Disclosure

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 16.0 Affected

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CVE-2026-53228 vulnerability details – vuln.today
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