# CVE-2025-40028: binder: fix double-free in dbitmap

> A double-free vulnerability in the Linux kernel binder driver allows local attackers to cause denial of service or potentially escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Oct 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40028, DEBIAN-CVE-2025-40028, GHSA-8vjm-fc8f-c7jh, ROOT-OS-DEBIAN-13-CVE-2025-40028, UBUNTU-CVE-2025-40028

## What is CVE-2025-40028?

CVE-2025-40028 is a high-severity use after free vulnerability in Linux, published on 28 Oct 2025. 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:

binder: fix double-free in dbitmap

A process might fail to allocate a new bitmap when trying to expand its
proc->dmap. In that case, dbitmap_grow() fails and frees the old bitmap
via dbitmap_free(). However, the driver calls dbitmap_free() again when
the same process terminates, leading to a double-free error:

  ==================================================================
  BUG: KASAN: double-free in binder_proc_dec_tmpref+0x2e0/0x55c
  Free of addr ffff00000b7c1420 by task kworker/9:1/209

  CPU: 9 UID: 0 PID: 209 Comm: kworker/9:1 Not tainted 6.17.0-rc6-dirty #5 PREEMPT
  Hardware name: linux,dummy-virt (DT)
  Workqueue: events binder_deferred_func
  Call trace:
   kfree+0x164/0x31c
   binder_proc_dec_tmpref+0x2e0/0x55c
   binder_deferred_func+0xc24/0x1120
   process_one_work+0x520/0xba4
  [...]

  Allocated by task 448:
   __kmalloc_noprof+0x178/0x3c0
   bitmap_zalloc+0x24/0x30
   binder_open+0x14c/0xc10
  [...]

  Freed by task 449:
   kfree+0x184/0x31c
   binder_inc_ref_for_node+0xb44/0xe44
   binder_transaction+0x29b4/0x7fbc
   binder_thread_write+0x1708/0x442c
   binder_ioctl+0x1b50/0x2900
  [...]
  ==================================================================

Fix this issue by marking proc->map NULL in dbitmap_free().

## Which versions are affected by CVE-2025-40028?


## How do I fix CVE-2025-40028?

Apply the vendor's patch.

## Is CVE-2025-40028 being exploited?

There is no known exploitation of CVE-2025-40028 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40028 and fix it if it is affected.

What it is: CVE-2025-40028 is a high-severity use after free vulnerability in Linux, published on 28 Oct 2025. 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-2025-40028 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-2025-40028/ (Markdown: https://insights.sbomify.com/CVE-2025-40028/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40028
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40028
- OSV: https://osv.dev/vulnerability/CVE-2025-40028

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40028/
Summaries are generated and may contain mistakes; the official description above is the record.