CVE-2026-70368: Stunnel: stack-based out-of-bounds read/write in stunnel s_vlog via oversized log message
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.4%
EPSS score, percentile 28.9 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 6.5 Medium
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- from 5.68 to before 5.80
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Workaround (from the CVE record)
To mitigate this issue, avoid exposing stunnel services to untrusted clients. Restrict access to these services to trusted networks only.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 5.68 to before 5.80 |
Versions not listed are: unaffected.
| Status | Versions |
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Versions not listed are: affected.
| Status | Versions |
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Versions not listed are: unaffected.
| Status | Versions |
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Versions not listed are: unaffected.
| Status | Versions |
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Versions not listed are: affected.
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Versions not listed are: affected.
Source: CVE List, as of . About the data.
About this vulnerability
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…
Summary: CVE record, as of .
- CISA has not added CVE-2026-70368 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 4 Aug 2026.
- The CVE record carries a CVSS v3.1 base score of 6.5 (Medium), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.4% (percentile 28.9), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact partial.
- The credits in the CVE record name AISLE as finder.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
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".
Source: CVE List, as of . About the data.
Weakness
CWE-125
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |