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".
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mobi-Com Polska Sp. z o.o. | stunnel | 5.68 – < 5.80 | 5.80 |
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 6 | — | — |
| Red Hat | Red Hat Enterprise Linux 7 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | stunnel | 3:5.80-1 | — |
| Debian 13 | stunnel4 | No fix yet | — |
| Debian 12 | stunnel4 | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | stunnel | 5.70-150600.3.6.1 | SUSE-SU-2026:4617-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | stunnel | 5.74-160000.3.1 | SUSE-SU-2026:24232-1 |
| SLES 16.0 | stunnel | 5.74-160000.3.1 | SUSE-SU-2026:24232-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | stunnel | 5.80-1.1 | openSUSE-SU-2026:11500-1 |
| openSUSE Leap 16.0 | stunnel | 5.74-160000.3.1 | openSUSE-SU-2026:22088-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | stunnel | 5.82-r0 | — |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | stunnel | No fix yet | — |
Advisories 4
- SUSE-SU-2026:24232-1 Security update for stunnel SUSE / openSUSE Security Updates · Oct 21, 2026
- openSUSE-SU-2026:22088-1 Security update for stunnel SUSE / openSUSE Security Updates · Oct 19, 2026
- SUSE-SU-2026:4617-1 Security update for stunnel SUSE / openSUSE Security Updates · Oct 13, 2026
- openSUSE-SU-2026:11500-1 stunnel-5.80-1.1 on GA media SUSE / openSUSE Security Updates · Aug 12, 2026
References
- https://access.redhat.com/security/cve/CVE-2026-70368 vdb-entry
- RHBZ#2462029 issue-tracking