# CVE-2026-64525 — Linux

> As of 2026-07-25, CVE-2026-64525 is a vulnerability in Linux, EPSS 0.1% (5.2th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-64525 as of 2026-07-25; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-25

## What is CVE-2026-64525?

In the Linux kernel, the following vulnerability has been resolved: xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit The struct pernet_operations docstring in include/net/net_namespace.h explicitly warns against blocking RCU primitives in .exit handlers: Exit methods using blocking RCU primitives, such as synchronize_rcu(), should be implemented via exit_batch. [...] Please, avoid synchronize_rcu() at all, where it's possible. Note that a combination of pre_exit() and exit() can be used, since a synchronize_rcu() is guaranteed between the calls. xfrm_policy_fini() violates this: it calls synchronize_rcu() before freeing the policy_bydst hash tables (so no RCU reader is mid- traversal at free time), but runs from xfrm_net_ops.exit -- once per namespace -- so a cleanup_net() of N namespaces pays N full RCU grace periods serially. Use the documented pre_exit/exit split. Move the policy flush (and the workqueue drains it depends on) into a new .pre_exit handler; xfrm_policy_fini() then runs in .exit and frees the hash tables after the synchronize_rcu_expedited() that cleanup_net() guarantees between the two phases. Providing O(1) RCU grace periods per batch instead of O(N). Observed on Linux 6.18 with a workload doing unshare(CLONE_NEWNET) at ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread both stuck in xfrm_policy_fini()'s synchronize_rcu(), >300k struct net accumulated in the cleanup queue, Percpu in /proc/meminfo climbed to 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and __put_net counts were balanced, ruling out a refcount leak.

1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 72 days ago.

## Severity and exploitation probability

- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 5.2% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 0.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-25

## Is CVE-2026-64525 being exploited?

It currently carries a trending score of 31 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Linux](https://intel.threadlinqs.com/vendors/linux): Linux

## How to fix CVE-2026-64525

No vendor patch reference has been recorded for CVE-2026-64525 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-64525

No threat campaign in the Threadlinqs corpus currently references CVE-2026-64525, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-07-26. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [git.kernel.org](https://git.kernel.org/stable/c/bca6386dc08750fc7cdcbc7683473748ba3114b9)
- [git.kernel.org (91cc13978ab0bc6f669139f53e7e613a860d10e0)](https://git.kernel.org/stable/c/91cc13978ab0bc6f669139f53e7e613a860d10e0)
- [git.kernel.org (d14ae8ef88c2c6590e107db61b6adce148cec7b3)](https://git.kernel.org/stable/c/d14ae8ef88c2c6590e107db61b6adce148cec7b3)
- [git.kernel.org (3e52417318473782012b236d0325bf7d2266a597)](https://git.kernel.org/stable/c/3e52417318473782012b236d0325bf7d2266a597)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-64525
Full detection coverage and IOCs for threats exploiting CVE-2026-64525 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp