# CVE-2026-31602: ALSA: ctxfi: Limit PTP to a single page

> A local attacker can trigger a kernel page fault and system crash by exceeding memory limits in the ALSA ctxfi driver.

- **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:** 24 Apr 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-31602, DEBIAN-CVE-2026-31602, GHSA-426x-jc5h-fmgg, ROOT-OS-DEBIAN-11-CVE-2026-31602, ROOT-OS-DEBIAN-12-CVE-2026-31602, ROOT-OS-UBUNTU-2204-CVE-2026-31602, ROOT-OS-UBUNTU-2404-CVE-2026-31602, UBUNTU-CVE-2026-31602

## What is CVE-2026-31602?

CVE-2026-31602 is a high-severity memory corruption vulnerability in Linux kernel, published on 24 Apr 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:

ALSA: ctxfi: Limit PTP to a single page

Commit 391e69143d0a increased CT_PTP_NUM from 1 to 4 to support 256
playback streams, but the additional pages are not used by the card
correctly. The CT20K2 hardware already has multiple VMEM_PTPAL
registers, but using them separately would require refactoring the
entire virtual memory allocation logic.

ct_vm_map() always uses PTEs in vm->ptp[0].area regardless of
CT_PTP_NUM. On AMD64 systems, a single PTP covers 512 PTEs (2M). When
aggregate memory allocations exceed this limit, ct_vm_map() tries to
access beyond the allocated space and causes a page fault:

  BUG: unable to handle page fault for address: ffffd4ae8a10a000
  Oops: Oops: 0002 [#1] SMP PTI
  RIP: 0010:ct_vm_map+0x17c/0x280 [snd_ctxfi]
  Call Trace:
  atc_pcm_playback_prepare+0x225/0x3b0
  ct_pcm_playback_prepare+0x38/0x60
  snd_pcm_do_prepare+0x2f/0x50
  snd_pcm_action_single+0x36/0x90
  snd_pcm_action_nonatomic+0xbf/0xd0
  snd_pcm_ioctl+0x28/0x40
  __x64_sys_ioctl+0x97/0xe0
  do_syscall_64+0x81/0x610
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

Revert CT_PTP_NUM to 1. The 256 SRC_RESOURCE_NUM and playback_count
remain unchanged.

## Which versions are affected by CVE-2026-31602?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31602?

Apply the vendor's patch.

## Is CVE-2026-31602 being exploited?

There is no known exploitation of CVE-2026-31602 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31602 and fix it if it is affected.

What it is: CVE-2026-31602 is a high-severity memory corruption vulnerability in Linux kernel, published on 24 Apr 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-2026-31602 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-31602/ (Markdown: https://insights.sbomify.com/CVE-2026-31602/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31602
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31602
- OSV: https://osv.dev/vulnerability/CVE-2026-31602

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31602/
Summaries are generated and may contain mistakes; the official description above is the record.