---
id: CVE-2026-70368
title: >-
  Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized
  log message
summary: >-
  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 tri…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L'
cvssSource: cna
cwe:
  - CWE-125
vendor: Mobi-Com Polska Sp. z o.o.
product: stunnel
affected:
  - stunnel >= 5.68 < 5.80
  - stunnel (all versions)
  - stunnel
  - stunnel
  - stunnel (all versions)
  - stunnel (all versions)
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-08-04T14:21:17.494804Z'
published: '2026-08-04'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T22:51:55.471Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-70368'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-70368'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2462029'
    label: RHBZ#2462029
tags:
  - cve.org
epss: 0.00353
epssPercentile: 0.2915
ingestedAt: '2026-11-05T23:41:31.938Z'
---

## Overview

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".

## Affected

- `stunnel >= 5.68 < 5.80`
- `stunnel (all versions)`
- `stunnel`
- `stunnel`
- `stunnel (all versions)`
- `stunnel (all versions)`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

### Workarounds

To mitigate this issue, avoid exposing stunnel services to untrusted clients. Restrict access to these services to trusted networks only.