# CVE-2023-53702: s390/crypto: use vector instructions only if available for ChaCha20

> A missing hardware capability check in the s390 ChaCha20 implementation causes a kernel panic on systems without vector instructions.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Oct 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2023-53702, DEBIAN-CVE-2023-53702, GHSA-28rv-6x7m-q268, ROOT-OS-UBUNTU-2204-CVE-2023-53702, UBUNTU-CVE-2023-53702

## What is CVE-2023-53702?

CVE-2023-53702 is a denial of service vulnerability in Linux, published on 22 Oct 2025. 

### Official description

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

s390/crypto: use vector instructions only if available for ChaCha20

Commit 349d03ffd5f6 ("crypto: s390 - add crypto library interface for
ChaCha20") added a library interface to the s390 specific ChaCha20
implementation. However no check was added to verify if the required
facilities are installed before branching into the assembler code.

If compiled into the kernel, this will lead to the following crash,
if vector instructions are not available:

data exception: 0007 ilc:3 [#1] SMP
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.3.0-rc7+ #11
Hardware name: IBM 3931 A01 704 (KVM/Linux)
Krnl PSW : 0704e00180000000 000000001857277a (chacha20_vx+0x32/0x818)
           R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3
Krnl GPRS: 0000037f0000000a ffffffffffffff60 000000008184b000 0000000019f5c8e6
           0000000000000109 0000037fffb13c58 0000037fffb13c78 0000000019bb1780
           0000037fffb13c58 0000000019f5c8e6 000000008184b000 0000000000000109
           00000000802d8000 0000000000000109 0000000018571ebc 0000037fffb13718
Krnl Code: 000000001857276a: c07000b1f80b        larl    %r7,0000000019bb1780
           0000000018572770: a708000a            lhi     %r0,10
          #0000000018572774: e78950000c36        vlm     %v24,%v25,0(%r5),0
          >000000001857277a: e7a060000806        vl      %v26,0(%r6),0
           0000000018572780: e7bf70004c36        vlm     %v27,%v31,0(%r7),4
           0000000018572786: e70b00000456        vlr     %v0,%v27
           000000001857278c: e71800000456        vlr     %v1,%v24
           0000000018572792: e74b00000456        vlr     %v4,%v27
Call Trace:
 [<000000001857277a>] chacha20_vx+0x32/0x818
Last Breaking-Event-Address:
 [<0000000018571eb6>] chacha20_crypt_s390.constprop.0+0x6e/0xd8
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

Fix this by adding a missing MACHINE_HAS_VX check.

[agordeev@linux.ibm.com: remove duplicates in commit message]

## Which versions are affected by CVE-2023-53702?


## How do I fix CVE-2023-53702?

Apply the vendor's patch.

## Is CVE-2023-53702 being exploited?

There is no known exploitation of CVE-2023-53702 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-53702 and fix it if it is affected.

What it is: CVE-2023-53702 is a denial of service vulnerability in Linux, published on 22 Oct 2025. 
Exploitation: There is no known exploitation of CVE-2023-53702 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-2023-53702/ (Markdown: https://insights.sbomify.com/CVE-2023-53702/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53702
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53702
- OSV: https://osv.dev/vulnerability/CVE-2023-53702

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53702/
Summaries are generated and may contain mistakes; the official description above is the record.