Linux: Out-of-bounds Write

What to do

1. Update Linux to ea9f65b27c8404e164848ebff1443310fd187629 or d6621f60192fe10c047a4487be42a6f4c150707f or 2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5 or a0c4ce9900a108eaf55d0f3b399cb55999647d39, whichever matches your release line, or a later version.
2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.168 or 6.6.134, whichever matches your release line, or a later version.
3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

Version data comes from the organisation that assigned the CVE; 4 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector

NetworkCan be exploited remotely over a network, including the internet.

Attack complexity

LowNo special conditions are needed; the attack works reliably.

Privileges required

NoneNo account or login is needed.

User interaction

NoneNo action by a victim is required.

Scope

UnchangedImpact stays within the vulnerable component.

Confidentiality

HighAll data handled by the component can be read.

Integrity

HighData or code can be modified at will.

Availability

HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: clear skb2->cb[] in ip4ip6_err() Oskar Kjos reported the following problem. ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written by the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes IPCB(skb2) to __ip_options_echo(), which interprets that cb[] region as struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff at offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr value. __ip_options_echo() then reads optlen from attacker-controlled packet data at sptr[rr+1] and copies that many bytes into dopt->__data, a fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE). To fix this we clear skb2->cb[], as suggested by Oskar Kjos. Also add minimal IPv4 header validation (version == 4, ihl >= 5).

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

Timeline

1. May 1, 2026CVE record published.
2. October 16, 2026CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
3. November 11, 2026Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

• 7.5 High severity

  Red Hat Enterprise Linux 10: Out-of-bounds Write

  CVE-2026-37457May 1, 2026Red Hat
• 7.8 High severity

  Linux: Out-of-bounds Write

  CVE-2026-43047May 1, 2026Linux
• 9.8 Critical severity

  Linux: Out-of-bounds Write

  CVE-2026-43038May 1, 2026Linux
• 7.8 High severity

  Linux: Out-of-bounds Write

  CVE-2026-43020May 1, 2026Linux
• 7.8 High severity

  Linux: Out-of-bounds Write

  CVE-2026-31780May 1, 2026Linux
• 7.8 High severity

  Linux: Out-of-bounds Write

  CVE-2026-31772May 1, 2026Linux

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