CVE-2026-52937: tap: fix stack info leak in tap_ioctl() SIOCGIFHWADDR

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-24 · updated 2026-10-30
Weakness: CWE-401

Description

In the Linux kernel, the following vulnerability has been resolved: tap: fix stack info leak in tap_ioctl() SIOCGIFHWADDR In the SIOCGIFHWADDR path, tap_ioctl() copies 16 bytes of an uninitialised on-stack struct sockaddr_storage to userspace via ifr_hwaddr, but netif_get_mac_address() only writes sa_family and dev->addr_len (6 for Ethernet) bytes, leaving sa_data[6..13] uninitialised. Those 8 trailing bytes leak kernel stack contents; SIOCGIFHWADDR on a macvtap chardev returns kernel .text and direct-map pointers, defeating KASLR. Initialise ss at declaration.

Affected products

Linux kernel: from 5.4.103 before 5.5; from 5.10.21 before 5.11; from 5.11.4 before 6.18.34; from 6.19 before 7.0.11; 7.1-rc1, 7.1-rc2, 7.1-rc3, 7.1-rc4 — fixed in 5.5, 5.11, 6.18.34, 7.0.11
Linux: from 5.4.103 before 5.5; from 5.10.21 before 5.11; from 5.11.4 before 5.12 — fixed in 5.5, 5.11, 5.12

How to fix

Upgrade to a fixed version: Linux kernel 5.5, 5.11, 6.18.34, 7.0.11; Linux 5.5, 5.11, 5.12. Check the vendor advisory for mitigations.

References

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