---
id: CVE-2026-74314
title: 'bpf: Cancel special fields on map value recycle'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Cancel special fields on map value recycle

  Map update and delete paths currently call bpf_obj_free_fields() when a
  value is being replaced or recycled. That makes…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 14a324f6a67ef6a53e04362a70160a47eb8afffa <
    9ea734e2cc0143d7429ab7dc0b20c85e5836183c
  - >-
    Linux >= 14a324f6a67ef6a53e04362a70160a47eb8afffa <
    a3a81d247651218e47153f2d2afd7aee236726fd
  - Linux f0462d38589422bc9e27fd3c6343dfeb6b3db2f9
  - Linux >= 5.18.18 < 5.19
  - Linux 5.19
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T18:53:09.033904Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:55:32.490Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-74314'
references:
  - url: 'https://git.kernel.org/stable/c/9ea734e2cc0143d7429ab7dc0b20c85e5836183c'
  - url: 'https://git.kernel.org/stable/c/a3a81d247651218e47153f2d2afd7aee236726fd'
tags:
  - cve.org
epss: 0.00177
epssPercentile: 0.06771
ingestedAt: '2026-10-16T19:46:24.380Z'
---

## Overview

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

bpf: Cancel special fields on map value recycle

Map update and delete paths currently call bpf_obj_free_fields() when a
value is being replaced or recycled. That makes field destruction depend
on the context of the update/delete operation. For tracing programs this
can include NMI context, where referenced kptr destructors, uptr
unpinning, and graph root destruction are not generally safe.

Introduce bpf_obj_cancel_fields() for the reusable-value path. It only
performs NMI-safe cleanup for timer, workqueue, and task_work fields.
Fields that need full destruction are left attached to the recycled value
and are destroyed by the final cleanup path instead.

Switch array and hashtab update/delete/recycle paths to this cancel
helper. Keep bpf_obj_free_fields() for final map destruction and for
bpf_mem_alloc destructors. Preallocated hashtabs do not have allocator
destructors, so teardown continues to walk the normal and extra elements
and fully destroy their fields.

This deliberately relaxes the eager-free semantics of map update/delete
for special fields. Programs that relied on a recycled map slot becoming
empty immediately after update/delete were relying on behavior that
cannot be implemented safely from every BPF execution context without
offloading arbitrary destructors.

There is a chance this change breaks programs making assumptions
regarding the eager freeing of fields. If so, we can relax semantics to
cancellation only when irqs_disabled() is true in the future. However,
theoretically, map values that get reused eagerly already have weaker
guarantees as parallel users can recreate freed fields before the new
element becomes visible again.

## Affected

- `Linux >= 14a324f6a67ef6a53e04362a70160a47eb8afffa < 9ea734e2cc0143d7429ab7dc0b20c85e5836183c`
- `Linux >= 14a324f6a67ef6a53e04362a70160a47eb8afffa < a3a81d247651218e47153f2d2afd7aee236726fd`
- `Linux f0462d38589422bc9e27fd3c6343dfeb6b3db2f9`
- `Linux >= 5.18.18 < 5.19`
- `Linux 5.19`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.