CVE-2026-70368
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".
CSIRTS triage
- What
- A stack-based buffer overflow in Stunnel's logging function allows out-of-bounds read/write when processing oversized log messages.
- Who is affected
- Stunnel installations with custom logging enabled or exposed to oversized log inputs.
- Urgency
- Medium severity with CVSS 6.5; memory corruption can lead to code execution or denial of service.
- Action
- Upgrade Stunnel to the patched version or limit log message size via configuration.
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Exploitation outlook
- Low exploitation risk0.35% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 28% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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