CVE-2026-70368
Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message
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".
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
6.5
Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message
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".
- Record
CVE-2026-70368- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Weakness
- CWE-125
- Updated
- 2026-11-05
EUVDEUVD-2026-52688
6.5
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".
- Record
EUVD-2026-52688- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Updated
- 2026-11-06
GitHub AdvisoriesGHSA-g6w9-m7h7-wgq9
6.5
A stack-based out-of-bounds read vulnerability exists in the "s_vlog" function of stunnel, when...
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".
- Record
GHSA-g6w9-m7h7-wgq9- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Weakness
- CWE-125
- Updated
- 2026-11-02
NVD
6.5
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".
- Record
CVE-2026-70368- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Weakness
- CWE-125
- Updated
- 2026-11-06
OSVALPINE-CVE-2026-70368
6.5
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".
- Record
ALPINE-CVE-2026-70368- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Updated
- 2026-11-03
OSV
6.5
Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message
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".
- Record
CVE-2026-70368- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Weakness
- CWE-125
- Updated
- 2026-11-07
Show 7 moreShow less
OSVDEBIAN-CVE-2026-70368
6.5
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".
- Record
DEBIAN-CVE-2026-70368- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L - Updated
- 2026-11-02
OSVAZL-94574 No score
CVE-2026-70368 affecting package stunnel 5.74-1
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".
- Record
AZL-94574- Updated
- 2026-11-05
OSVMGASA-2026-0575 No score
Updated stunnel package fixes security vulnerabilities
Localhost-filter bypass in SOCKS server mode. (CVE-2026-70367) Out-of-bounds memory access when logging long protocol messages. (CVE-2026-70368)
- Record
MGASA-2026-0575- Updated
- 2026-11-05
OSVopenSUSE-SU-2026:11500-1 No score
stunnel-5.80-1.1 on GA media
These are all security issues fixed in the stunnel-5.80-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:11500-1- Updated
- 2026-11-02
OSVopenSUSE-SU-2026:22088-1 No score
Security update for stunnel
This update for stunnel fixes the following issues:
- CVE-2026-70367: incomplete IP address filtering in SOCKS proxy mode can allow localhost restriction bypasses (bsc#1274207).
- CVE-2026-70368: oversized log messages in logging routines can cause stack out-of-bounds reads (bsc#1274206).
- Record
openSUSE-SU-2026:22088-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:24232-1 No score
Security update for stunnel
This update for stunnel fixes the following issues:
- CVE-2026-70367: incomplete IP address filtering in SOCKS proxy mode can allow localhost restriction bypasses (bsc#1274207).
- CVE-2026-70368: oversized log messages in logging routines can cause stack out-of-bounds reads (bsc#1274206).
- Record
SUSE-SU-2026:24232-1- Updated
- 2026-11-02
OSVSUSE-SU-2026:4617-1 No score
Security update for stunnel
This update for stunnel fixes the following issues:
- CVE-2026-70367: incomplete IP address filtering in SOCKS proxy mode can allow localhost restriction bypasses (bsc#1274207).
- CVE-2026-70368: oversized log messages in logging routines can cause stack out-of-bounds reads (bsc#1274206).
- Record
SUSE-SU-2026:4617-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
stunnelAlpine:v3.24 |
before 5.82-r0 | 5.82-r0 |
stunnelAzure Linux:3 |
through 5.74-1 | None known |
stunnelDebian:14 |
before 3:5.80-1, plus listed versions 2:3.26-102:3.26-112:3.26-22:3.26-2.12:3.26-3 Show 15 moreShow less2:3.26-42:3.26-52:3.26-62:3.26-72:3.26-82:3.26-92:3.26-dfsg-12:3.26-dfsg-23.10-0potato13.22-13:5.78-33:5.78-43:5.78-53:5.79-13:5.79-2 |
3:5.80-1 |
stunnel4Debian:12 |
All versions, plus listed versions 3:5.68-23:5.68-2+deb12u13:5.70-13:5.70-23:5.72-1 Show 10 moreShow less3:5.72-23:5.72-33:5.72-43:5.73-13:5.74-13:5.74-23:5.76-13:5.77-13:5.78-13:5.78-2 |
None known |
stunnel4Debian:13 |
All versions, plus listed versions 3:5.74-23:5.76-13:5.77-13:5.78-13:5.78-2 |
None known |
stunnelMageia:10 From an advisory covering 2 CVEs |
before 5.80-1.mga10 | 5.80-1.mga10 |
stunnelSUSE:Linux Enterprise Server 16.0 From an advisory covering 2 CVEs |
before 5.74-160000.3.1 | 5.74-160000.3.1 |
stunnelSUSE:Linux Enterprise Server for SAP applications 16.0 From an advisory covering 2 CVEs |
before 5.74-160000.3.1 | 5.74-160000.3.1 |
stunnelSUSE:Linux Enterprise Module for Server Applications 15 SP7 From an advisory covering 2 CVEs |
before 5.70-150600.3.6.1 | 5.70-150600.3.6.1 |
stunnelopenSUSE:Tumbleweed From an advisory covering 2 CVEs |
before 5.80-1.1 | 5.80-1.1 |
stunnelopenSUSE:Leap 16.0 From an advisory covering 2 CVEs |
before 5.74-160000.3.1 | 5.74-160000.3.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | CVE List, EUVD, NVD, OSV | |
| affected, aliases, facts, references | OSV | |
| affected, aliases, references | OSV | |
| affected, aliases, products, published, references | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-70368 is a medium vulnerability (CVSS 6.5) in Microsoft Stunnel, published August 4, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.35%, the 29th percentile. Fixed in stunnel 5.82-r0.
References
access.redhat.com/security/cve/CVE-2026-70368
bugzilla.redhat.com/show_bug.cgi?id=2462029
nvd.nist.gov/vuln/detail/CVE-2026-70368
github.com/advisories/GHSA-g6w9-m7h7-wgq9
security.alpinelinux.org/vuln/CVE-2026-70368
access.redhat.com/downloads/content/package-browser
Show 16 moreShow less
github.com/CVEProject/cvelistV5/tree/main/cves/2026/70xxx/CVE-2026-70368.json
github.com/mtrojnar/stunnel
security-tracker.debian.org/tracker/CVE-2026-70368
advisories.mageia.org/MGASA-2026-0575.html
bugs.mageia.org/show_bug.cgi?id=36183
lists.opensuse.org/archives/list/[email protected]/message/472TIVLEO2YOJZVNWJR6RWFE3SX4M7P6
bugzilla.redhat.com/show_bug.cgi?id=2462083
stunnel.org/CVE-2026-70367.html
stunnel.org/CVE-2026-70368.html
lists.fedoraproject.org/archives/list/[email protected]/message/IX766E4H5ND5VOKDYVM2E2GUCKKG6EDD
suse.com/support/update/announcement/2026/suse-su-202624232-1
bugzilla.suse.com/1274206
bugzilla.suse.com/1274207
suse.com/security/cve/CVE-2026-70367
suse.com/security/cve/CVE-2026-70368
suse.com/support/update/announcement/2026/suse-su-20264617-1