# CVE-2026-64579: xfrm: policy: preallocate inexact bins before xfrm_hash_rebuild reinsert

> A logic error in Linux kernel xfrm policy rebuilding causes a general protection fault and kernel panic under memory pressure, leading to denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** AZL-94458, BELL-CVE-2026-64579, DEBIAN-CVE-2026-64579, GHSA-4969-9gf7-vmr2, UBUNTU-CVE-2026-64579

## What is CVE-2026-64579?

CVE-2026-64579 is a vulnerability in Linux, published on 5 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

xfrm: policy: preallocate inexact bins before xfrm_hash_rebuild reinsert

xfrm_hash_rebuild()'s first loop preallocates the bins/chains the reinsert
loop needs, so the reinsert (after hlist_del_rcu()) cannot allocate or
fail. But its guard is inverted: it skips policies with prefixlen <
threshold and preallocates for the rest.

prefixlen < threshold is exactly when policy_hash_bysel() returns NULL and
the reinsert takes the allocating xfrm_policy_inexact_insert() path. So the
loop preallocates for the exact policies (which never allocate) and skips
the inexact ones, whose bin/node is then allocated GFP_ATOMIC during
reinsert. On failure the error path only WARN_ONCE()s and continues,
leaving a poisoned bydst node; the next rebuild's hlist_del_rcu()
dereferences LIST_POISON2 and takes a GPF. Reachable under memory pressure,
deterministic via failslab.

Invert the guard so preallocation covers exactly the reinserted policies;
the reinsert then allocates nothing and cannot fail.

Crash:
  Oops: general protection fault, probably for non-canonical address
  0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI
  KASAN: maybe wild-memory-access in range [0xdead...]
  ...
  Workqueue: events xfrm_hash_rebuild
  RIP: 0010:xfrm_hash_rebuild+0x5b3/0x1190
  RAX: dead000000000122   (LIST_POISON2 + offset)
  ...
  Call Trace:
   hlist_del_rcu (include/linux/rculist.h:599)
   xfrm_hash_rebuild (net/xfrm/xfrm_policy.c:1365)
   process_one_work (kernel/workqueue.c:3322)
   worker_thread (kernel/workqueue.c:3486)
   kthread (kernel/kthread.c:436)
   ret_from_fork (arch/x86/kernel/process.c:158)
   ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
   ...
  Kernel panic - not syncing: Fatal exception in interrupt

## Which versions are affected by CVE-2026-64579?


## How do I fix CVE-2026-64579?

Apply the vendor's patch.

## Is CVE-2026-64579 being exploited?

There is no known exploitation of CVE-2026-64579 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64579 and fix it if it is affected.

What it is: CVE-2026-64579 is a vulnerability in Linux, published on 5 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64579 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64579/ (Markdown: https://insights.sbomify.com/CVE-2026-64579/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64579
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64579
- OSV: https://osv.dev/vulnerability/CVE-2026-64579

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64579/
Summaries are generated and may contain mistakes; the official description above is the record.