CVE-2026-72019 macsec: don't read an unset MAC header in macsec_encrypt()
An out-of-bounds read in the Linux kernel MACsec module allows attackers to leak heap memory or cause a crash via crafted network packets.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72019?
CVE-2026-72019 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
macsec: don't read an unset MAC header in macsec_encrypt()
macsec_encrypt() reads the Ethernet header via eth_hdr(skb) (skb->head + skb->mac_header) to memmove() the 12 source/destination MAC bytes forward and make room for the SecTAG.
On the AF_PACKET SOCK_RAW + PACKET_QDISC_BYPASS transmit path the skb reaches the macsec ndo_start_xmit() with the MAC header unset, so eth_hdr(skb) resolves to skb->head + (u16)~0 and the read is out of bounds: a 12-byte heap over-read that is also emitted on the wire as the frame's outer source/destination MAC. KASAN reports a slab-out-of-bounds read in macsec_start_xmit() on 6.0; on current mainline a CONFIG_DEBUG_NET build flags it as an unset mac header in skb_mac_header().
On the TX path the L2 header is at skb->data, so use skb_eth_hdr(), added by commit 96cc4b69581d ("macvlan: do not assume mac_header is set in macvlan_broadcast()") for exactly this purpose.
Weakness: CWE-125
Which versions are affected by CVE-2026-72019?
How do I fix CVE-2026-72019?
Apply the vendor's patch.
Is CVE-2026-72019 being exploited?
There is no known exploitation of CVE-2026-72019 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72019, DEBIAN-CVE-2026-72019, GHSA-593p-5684-69pq, UBUNTU-CVE-2026-72019.