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Fencer Vulns
medium 6.5

CVE-2026-70368 json

Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message

published 2026-08-04 3 mo ago modified 2026-11-05 3 d ago also EUVD-2026-52688

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits
0
none known

Summary

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".

Patch / fix

  • Mobi-Com Polska Sp. z o.o. stunnel 5.80
  • stunnel Debian 14 3:5.80-1

debian advisories DEBIAN-CVE-2026-70368

  • stunnel SLES for SAP applications 16.0, SLES 16.0 5.74-160000.3.1
  • stunnel SLE Module for Server Applications 15 SP7 5.70-150600.3.6.1

suse advisories SUSE-SU-2026:24232-1SUSE-SU-2026:4617-1

  • stunnel openSUSE Leap 16.0 5.74-160000.3.1
  • stunnel openSUSE Tumbleweed 5.80-1.1

opensuse advisories openSUSE-SU-2026:22088-1openSUSE-SU-2026:11500-1

  • stunnel Alpine 3.24 5.82-r0

alpine advisories ALPINE-CVE-2026-70368

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-70368 updated cvss 6.5

stunnel: Stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message

  • Red Hat Enterprise Linux 8 stunnel Red Hat Enterprise Linux 9 stunnel Red Hat Enterprise Linux 10 stunnel
    affected: workaround, no fix available “To mitigate this issue, avoid exposing stunnel services to untrusted clients. Restrict access to these services to trusted networks only.”
  • Red Hat Enterprise Linux 6 stunnel Red Hat Enterprise Linux 7 stunnel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Affected products

  • Mobi-Com Polska Sp. z o.o. stunnel
  • 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

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.