Critical

CVE-2026-74743 — macvlan: inherit needed_headroom and needed_tailroom from lowerdev

In the Linux kernel, the following vulnerability has been resolved: macvlan: inherit needed_headroom and needed_tailroom from lowerdev macvlan devices inherit hard_header_len from lowerdev during macvlan_init(), but leave needed_headroom and needed_tailroom set to 0. When the underlying lowerdev requires extra headroom or tailroom for headers/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx headroom), upper layers calculating packet headroom and tailroom fail to reserve sufficient space. This can result in reallocation overhead, skb headroom underflows, or KASAN slab-use-after-free crashes when dev_hard_header() / macvlan_hard_header() prepends header data or when lower devices append tailroom. Fix this by: 1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init(). 2. Propagating needed_headroom and needed_tailroom updates to attached macvlans in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.

Published Aug 26, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

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

Technical severity (critical)+10

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

—

No EPSS score.

Affects

Linux

CVSS base

9.8

Critical · 2 source(s)

Remediation

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

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

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.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < c2ef3f134b069c54b9cc95cce1a16c38c4939336≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < 7b0eb3e0f363ca79a3af9efd2e87c6258f11da2b≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < 8cd90e850e434577bf6774778657d26d6995e53f≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < 28afc87bd8da0b3348bbbd834c8a89e83712cf5e≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < 8f6a05dbac05725e0786701eb04778c5bdbe4eaa≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < 96fa90b74385b7f2b0d97251dd43d5ee6ca44668≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < bc9a00fb78e32bccc39d763bfd13a450705bac5d≥ b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 and < cef51860becd9700217c81732ca1eb1ea6ed6fe1 and 1 more version 2.6.23	Vulnerable	CVE Program (cve.org) e CISA ADP

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.

Score	Version	Severity	Expl.	Impact	Scored 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)

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

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 9.8
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Aug 26, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

8 on the record

git.kernel.org/stable/c/c2ef3f134b069c54b9cc95cce1a16c38c4939336
NIST National Vulnerability Database
git.kernel.org/stable/c/bc9a00fb78e32bccc39d763bfd13a450705bac5d
NIST National Vulnerability Database
git.kernel.org/stable/c/8cd90e850e434577bf6774778657d26d6995e53f
NIST National Vulnerability Database
git.kernel.org/stable/c/cef51860becd9700217c81732ca1eb1ea6ed6fe1
NIST National Vulnerability Database
git.kernel.org/stable/c/8f6a05dbac05725e0786701eb04778c5bdbe4eaa
NIST National Vulnerability Database
git.kernel.org/stable/c/28afc87bd8da0b3348bbbd834c8a89e83712cf5e
NIST National Vulnerability Database
git.kernel.org/stable/c/7b0eb3e0f363ca79a3af9efd2e87c6258f11da2b
NIST National Vulnerability Database
git.kernel.org/stable/c/96fa90b74385b7f2b0d97251dd43d5ee6ca44668
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 12h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 12h
Unknown CVE-2026-98428 ALSA: usb: 6fire: Avoid embedded URBs 1d
Unknown CVE-2026-98431 RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency 1d
Unknown CVE-2026-98430 RDMA/efa: Keep admin queues alive while IRQ is registered 1d
Unknown CVE-2026-98429 RDMA/efa: Keep EQ resources alive while IRQ is registered 1d

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 FIRST EPSS score.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
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-2026-74743 is "macvlan: inherit needed_headroom and needed_tailroom from lowerdev", 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. 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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