# CVE-2026-70368: Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message

> A remote attacker can cause a crash in stunnel by sending oversized log messages, triggering a stack-based out-of-bounds read.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Aug 2026
- **Updated:** 6 Aug 2026
- **Also known as:** AZL-94574, DEBIAN-CVE-2026-70368, ECHO-3040-3d7b-9a98, GHSA-g6w9-m7h7-wgq9

## What is CVE-2026-70368?

CVE-2026-70368 is a medium-severity memory corruption vulnerability in Mobi-Com Polska Sp. z o.o. Red Hat Enterprise Linux 10, published on 4 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A stack-based out-of-bounds read vulnerability exists in the "s_vlog" function of stunnel, when handling oversized log messages via "vsnprintf". A remote attacker with network access to a stunnel service can send protocol inputs that trigger a log message longer than 1024 bytes, leading to an out-of-bounds stack read and a potential crash. In certain corner cases, the same vulnerability could be used to replace a series of trailing "\n" characters with "\0".

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

## Which versions are affected by CVE-2026-70368?


## How do I fix CVE-2026-70368?

Apply the vendor's patch.

## Is CVE-2026-70368 being exploited?

There is no known exploitation of CVE-2026-70368 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-70368 and fix it if it is affected.

What it is: CVE-2026-70368 is a medium-severity memory corruption vulnerability in Mobi-Com Polska Sp. z o.o. Red Hat Enterprise Linux 10, published on 4 Aug 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-2026-70368 in the wild and no public exploit code.

Affected product: Mobi-Com Polska Sp. z o.o. Red Hat Enterprise Linux 10. 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-2026-70368/ (Markdown: https://insights.sbomify.com/CVE-2026-70368/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70368
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70368
- OSV: https://osv.dev/vulnerability/CVE-2026-70368

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-70368/
Summaries are generated and may contain mistakes; the official description above is the record.