Out-of-bounds Read in Mobi-Com Polska Sp. Z O.o. Stunnel

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".

Vulnerability class: Buffer Overflow

EPSS: 0.004 (28.8th percentile) — read the EPSS interpretation.