CVE Intelligence
Critical

CVE-2026-53228 — Linux kernel SIT tunnel: stale header pointer after GSO offload

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.

Published Jun 25, 2026 · Updated Oct 16, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.6% (30-day exploitation probability)+7
  • Technical severity (critical)+10
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.58%
ahead of 46% of scored CVEs · Oct 15, 2026
Affects
Linux
Linux and 1 more
CVSS base
9.8
Critical · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)
  • Documented patch — git.kernel.org (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Linux Linux version 3.18≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < f0e42f0c4337b1f220de1ddd63f47197c7dee4de≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < cb658c2f5f7977c2a1c77c9f239f4bc8196edb5c≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < 2fa49b2715e1bad12ce3b0fa64e234d9582c8193≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < 59f80c919713250fe5d25a4d9aea4e49580fa1d4≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < 0bfa7bba1f41aaf5f0604dc712bb4701493e3aa0≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < 9c67b44edb3598d234efae6e44649eb993c03da5≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < 1132e5edc2866c3530be17622153a597095f0e43
and 1 more ≥ 14909664e4e192f4c6f6fcdccd9919af7cf783ab and < fddd41445a0537b093e6b3f6232c9933cad1e48b
Vulnerable CVE Program (cve.org) e CISA ADP
Linux Linux Kernel version 7.1-rc5version 7.1-rc7version 7.1-rc6≥ 3.18 and < 5.10.259version 7.1-rc4version 7.1-rc3version 7.1-rc2version 7.1-rc1
and 6 more ≥ 6.19 and < 7.0.13≥ 6.13 and < 6.18.36≥ 6.7 and < 6.12.94≥ 6.2 and < 6.6.143≥ 5.16 and < 6.1.176≥ 5.11 and < 5.15.210
Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
9.8 CVSS 3.1 Critical 3.9 5.9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
9.8 CVSS 3.1 Critical — — Linux via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.58%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
web/proxy/WAF logsnetwork IDS/IPS

Analysis and videos

CVE-2026-53228: Linux kernel SIT tunnel: stale header pointer after GSO offload
CVE-2026-53228 is a critical issue in the Linux kernel SIT tunnel path for IPv6 over IPv4, rated 9.8 by the CNA under CVSS 3.1. The transmit function keeps using an inner IPv6 header pointer after a helper that can move the packet head, which may lead to reads from freed memory. Stable kernel fixes are referenced in the record, and no confirmed active exploitation appears in the sources consulted.

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 16, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · Analyzed → Modified
    Oct 15, 2026 · NIST National Vulnerability Database
  • Affected products added · linux/linux
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 9.8
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Jun 25, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 15, 2026 – Oct 15, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

9 on the record

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

  • CVE-2026-99999 ipv4: validate checksum_start before completing checksum 1d
  • CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 1d
  • CVE-2026-98431 RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency 2d
  • CVE-2026-98430 RDMA/efa: Keep admin queues alive while IRQ is registered 2d
  • CVE-2026-98429 RDMA/efa: Keep EQ resources alive while IRQ is registered 2d
  • CVE-2026-98428 ALSA: usb: 6fire: Avoid embedded URBs 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No CWE classification.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-53228 is "Linux kernel SIT tunnel: stale header pointer after GSO offload", rated Critical. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. EPSS 0.58% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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