# CVE-2026-88840: Busybox: busybox: tls ssl_server reads one byte out of bounds when parsing truncated clienthello

> An out-of-bounds read in BusyBox TLS server allows attackers to cause denial of service or potentially execute code via truncated ClientHello messages.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Sep 2026
- **Updated:** 26 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-88840, ECHO-0f33-f9b7-76c3, GHSA-w878-vhh4-m5pv, UBUNTU-CVE-2026-88840

## What is CVE-2026-88840?

CVE-2026-88840 is a medium-severity memory corruption vulnerability in Red Hat Hardened Images, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

BusyBox TLS get_client_hello() reads past the end of the input buffer when parsing a truncated ClientHello message.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-88840?


## How do I fix CVE-2026-88840?

No fix has been published for CVE-2026-88840 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-88840 being exploited?

There is no known exploitation of CVE-2026-88840 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-88840 and fix it if it is affected.

What it is: CVE-2026-88840 is a medium-severity memory corruption vulnerability in Red Hat Hardened Images, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-88840 in the wild and no public exploit code.

Affected product: Red Hat Hardened Images. 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-2026-88840/ (Markdown: https://insights.sbomify.com/CVE-2026-88840/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88840
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88840
- OSV: https://osv.dev/vulnerability/CVE-2026-88840

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-88840/
Summaries are generated and may contain mistakes; the official description above is the record.