Bug 2492102 (CVE-2026-52937)

Summary: CVE-2026-52937 kernel: tap: fix stack info leak in tap_ioctl() SIOCGIFHWADDR
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's tap driver. This vulnerability allows an attacker to potentially disclose sensitive kernel stack memory contents to userspace. The flaw occurs in the `tap_ioctl()` function when handling the `SIOCGIFHWADDR` command, where uninitialized portions of a stack-allocated structure are copied to userspace. This information leak could be used to bypass Kernel Address Space Layout Randomization (KASLR), making it easier for attackers to exploit other vulnerabilities.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-06-24 08:02:07 UTC 
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.
Comment 1 Mauro Matteo Cascella 2026-06-24 10:41:22 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062434-CVE-2026-52937-62eb@gregkh/T