---
cve: "CVE-2026-64416"
severity: "LOW"
cvss: 3.1
epss: "17%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-07-25 10:17:25"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-08T20:59:59+02:00"
---

# CVE-2026-64416

> 3.1 LOW

## Beschreibung

In the Linux kernel, the following vulnerability has been resolved:

mm: swap_cgroup: fix NULL deref in lookup_swap_cgroup_id on swapless host

lookup_swap_cgroup_id() passes swap_cgroup_ctrl[type].map to
__swap_cgroup_id_lookup() without checking that the type was ever
registered via swap_cgroup_swapon().  On a swapless host every ctrl->map
is NULL, so __swap_cgroup_id_lookup() dereferences NULL + a scaled
swp_offset().

Since commit bea67dcc5eea ("mm: attempt to batch free swap entries for
zap_pte_range()"), zap_pte_range() -> swap_pte_batch() calls
lookup_swap_cgroup_id() on any non-present, non-none PTE that decodes as a
real swap entry, without first validating it against swap_info[].  A
single PTE corrupted into a type-0 swap entry takes the host down at
process exit.

We hit this in production on a swapless 6.12.58 host: ~1s of
"get_swap_device: Bad swap file entry 3f800204222bb" (do_swap_page() being
correctly defensive about the same entry) followed by

  BUG: unable to handle page fault for address: 000003f800204220
  RIP: 0010:lookup_swap_cgroup_id+0x2b/0x60
  Call Trace:
   swap_pte_batch+0xbf/0x230
   zap_pte_range+0x4c8/0x780
   unmap_page_range+0x190/0x3e0
   exit_mmap+0xd9/0x3c0
   do_exit+0x20c/0x4b0

syzbot has reported the identical stack.

The source of the PTE corruption is a separate bug; this change makes the
teardown path as robust as the fault path already is.  Every other caller
of lookup_swap_cgroup_id() is downstream of a get_swap_device() that has
already validated the entry, so the new branch is cold.

## Patch verfügbar (OSV)

- Kernel ≥ 6.12.97
- Kernel ≥ 6.18.39
- Kernel ≥ 7.1.4

## Referenzen

- <https://git.kernel.org/stable/c/818416fef38759f23210de449663cd9d7e293d39>
- <https://git.kernel.org/stable/c/b415c00bf23df577a4a95673d00ae76687bcc1d4>
- <https://git.kernel.org/stable/c/6a4196d19f477524d2f92adca90fc1fbe9a0420a>
- <https://git.kernel.org/stable/c/63b02a9409cb5180398491b093e48bcb5315f5fb>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-64416) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_