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Linux KernelOperating system · Linux

CVE-2026-23209

HIGH · 7.8 CVSS v3.1 Published 2026-02-14
Fix available
A fix is available. Upgrade to 5.10.250 / 5.15.200 or later.
See remediation →
80/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: macvlan: fix error recovery in macvlan_common_newlink() valis provided a nice repro to crash the kernel: ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2 ip link add mv0 link p2 type macvlan mode source ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20 ping -c1 -I p1 1.2.3.4 He also gave a very detailed analysis: <quote valis> The issue is triggered when a new macvlan link is created with MACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or MACVLAN_MACADDR_SET) parameter, lower device already has a macvlan port and register_netdevice() called from macvlan_common_newlink() fails (e.g. because of the invalid link name). In this case macvlan_hash_add_source is called from macvlan_change_sources() / macvlan_common_newlink(): This adds a reference to vlan to the port's vlan_source_hash using macvlan_source_entry. vlan is a pointer to the priv data of the link that is being created. When register_netdevice() fails, the error is returned from macvlan_newlink() to rtnl_newlink_create(): if (ops->newlink) err = ops->newlink(dev, &params, extack); else err = register_netdevice(dev); if (err < 0) { free_netdev(dev); goto out; } and free_netdev() is called, causing a kvfree() on the struct net_device that is still referenced in the source entry attached to the lower device's macvlan port. Now all packets sent on the macvlan port with a matching source mac address will trigger a use-after-free in macvlan_forward_source(). </quote valis> With all that, my fix is to make sure we call macvlan_flush_sources() regardless of @create value whenever "goto destroy_macvlan_port;" path is taken. Many thanks to valis for following up on this issue.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-416

Memory is used after it has been freed, so its contents — now potentially attacker-controlled — drive the program's behaviour. With careful heap grooming this becomes code execution. The fix requires disciplined ownership of memory and often a targeted rework of the object lifecycle.

General guidance for the use after free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 4.9.1, < 5.10.250>= 5.11, < 5.15.200>= 5.16, < 6.1.163>= 6.2, < 6.6.124>= 6.7, < 6.12.70>= 6.13, < 6.18.10= 4.9= 6.19

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.10.250 / 5.15.200 / 6.1.163 or later
Fixed in 5.10.2505.15.2006.1.163
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux kernel 5.10.250, 5.15.200, 6.1.163, or 6.6.124 (whichever series is applicable)

  1. 1. Identify the currently running Linux kernel version using `uname -r`
  2. 2. Determine which version range your current kernel falls into based on the affected ranges: >= 4.9.1 and < 5.10.250; >= 5.11 and < 5.15.200; >= 5.16 and < 6.1.163; >= 6.2 and < 6.6.124
  3. 3. If affected, plan for a kernel upgrade to a fixed release
  4. 4. For kernels in the 4.9.x - 5.10.x range, upgrade to 5.10.250 or later
  5. 5. For kernels in the 5.11 - 5.15.x range, upgrade to 5.15.200 or later
  6. 6. For kernels in the 5.16 - 6.1.x range, upgrade to 6.1.163 or later
  7. 7. For kernels in the 6.2 - 6.6.x range, upgrade to 6.6.124 or later
  8. 8. Apply the upgrade via your distribution's package manager (e.g., apt-get dist-upgrade, yum update, dnf upgrade) or compile a newer stable kernel
Caveat Kernel upgrades may introduce compatibility issues with custom modules or specific hardware drivers; thorough testing in a staging environment is recommended before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-23209 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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