CVE-2026-23209
medium
CVSS v3
—
CVSS v4 NEW
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VIR risk
5.5
Description
RHSA-2026:6037: kernel security update (Moderate)
Predictions
Exploit likelihood
20%
Patch ETA
—
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Mitigation details
Source: Debian Security Tracker · View original ↗ · DFSG
CVE-2026-23209 NameCVE-2026-23209 DescriptionIn 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…
CVE-2026-23209
| Name | CVE-2026-23209 |
| Description | 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, ¶ms, 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. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DLA-4498-1, DLA-4499-1, DSA-6141-1, DSA-6163-1 |
Vulnerable and fixed packages
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| linux (PTS) | bullseye | 5.10.223-1 | vulnerable |
| bullseye (security) | 5.10.257-1 | fixed | |
| bookworm | 6.1.170-3 | fixed | |
| bookworm (security) | 6.1.172-1 | fixed | |
| trixie | 6.12.86-1 | fixed | |
| trixie (security) | 6.12.90-1 | fixed | |
| forky | 7.0.9-1 | fixed | |
| sid | 7.0.10-1 | fixed | |
| linux-6.1 (PTS) | bullseye (security) | 6.1.174-1~deb11u1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| linux | source | bullseye | 5.10.251-1 | DLA-4498-1 | ||
| linux | source | bookworm | 6.1.164-1 | DSA-6163-1 | ||
| linux | source | trixie | 6.12.73-1 | DSA-6141-1 | ||
| linux | source | (unstable) | 6.18.10-1 | |||
| linux-6.1 | source | bullseye | 6.1.164-1~deb11u1 | DLA-4499-1 |
Notes
https://git.kernel.org/linus/f8db6475a83649689c087a8f52486fcc53e627e9 (6.19)
Apply commands
Notes
https://git.kernel.org/linus/f8db6475a83649689c087a8f52486fcc53e627e9 (6.19)OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| rocky | 8 | fixed | |
| rhel | 9 | fixed | |
| sles | affected | | |
| rocky | 9 | fixed | |
| debian | bookworm | fixed | 6.1.164-1 |
| debian | bullseye | fixed | 5.10.251-1 |
| debian | forky | fixed | 6.18.10-1 |
| debian | sid | fixed | 6.18.10-1 |
| debian | trixie | fixed | 6.12.73-1 |
| almalinux | 9 | fixed | kernel-devel-5.14.0-611.45.1.el9_7.aarch64.rpm |
| rhel | 8 | fixed | |
References
- https://errata.rockylinux.org/RLSA-2026:6036
- https://errata.rockylinux.org/RLSA-2026:6037
- https://access.redhat.com/errata/RHSA-2026:6153
- https://www.suse.com/security/cve/CVE-2026-23209.html
- https://errata.rockylinux.org/RLSA-2026:6153
- https://security-tracker.debian.org/tracker/CVE-2026-23209
- https://access.redhat.com/errata/RHSA-2026:6037
- https://bugzilla.redhat.com/2376376
- https://bugzilla.redhat.com/2439900
- https://bugzilla.redhat.com/2439931
- https://errata.almalinux.org/8/ALSA-2026-6037.html
- https://access.redhat.com/errata/RHSA-2026:6036
- https://errata.almalinux.org/8/ALSA-2026-6036.html
- https://bugzilla.redhat.com/2407333
- https://bugzilla.redhat.com/2439872
- https://bugzilla.redhat.com/2439886
- https://bugzilla.redhat.com/2439887
- https://bugzilla.redhat.com/2439947
- https://errata.almalinux.org/9/ALSA-2026-6153.html
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.