CVE-2026-70368: Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message
Vulnerability summary
CVE-2026-70368 is a medium (CVSS 6.5) Out-of-bounds Read vulnerability in mobi-com polska sp. z o.o. stunnel. EPSS estimates a 0.35% chance of exploitation in the next 30 days, higher than 29% of scored vulnerabilities.
Not severe (CVSS 6.5, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 4 · Related 4Timeline
- 04-08-2026PublishedVulnerability first disclosed.
- 06-08-2026Last modifiedVulnerability information updated.
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".
CVSS metrics
4 scores · 4 sources · 1 version- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
- OSV · AlpineEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
EPSS trend
Probability
0.35%
Chance of exploitation in the next 30 days
Percentile
29%
Versus all other CVEs
30-day change
Decrease -0.09 pp
From 0.44% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Debian2 products
- stunnel< 3:5.80-1
- stunnel4All versions (No fix recorded)
Alpine1 product
- stunnel< 5.82-r0
Mobi-com polska sp. z o.o.1 product
- stunnel≥ 5.68, < 5.80
3 vendors · 4 products
