Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message
CVE-2026-70368 is fixed in stunnel on 1 platform, first by DEBIAN-CVE-2026-70368, released August 8, 2026. It is not reported as exploited. Patch Radar priority: Routine.
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".
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| stunnel · Debian 14 | 3:5.80-1 | DEBIAN-CVE-2026-70368 | Aug 8, 2026 |
| stunnel · opensuse-leap 16.0 | 5.74-160000.3.1 | OPENSUSE-SU-2026:22088-1 | Nov 7, 2026 |
| stunnel · sles 15.7 | 5.70-150600.3.6.1 | SUSE-SU-2026:4617-1 | Nov 7, 2026 |
| stunnel · sles 16.0 | 5.74-160000.3.1 | SUSE-SU-2026:24232-1 | Nov 7, 2026 |
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