PatchSiren cyber security CVE debrief
CVE-2026-70368 stunnel CVE debrief
A stack-based out-of-bounds read vulnerability exists in stunnel's 's_vlog' function when handling oversized log messages via 'vsnprintf'. A remote attacker with network access to a stunnel service can send protocol inputs that trigger log messages longer than 1024 bytes, potentially leading to a crash or replacement of trailing 'n' characters with '0' in certain cases. The CVE record was published on 2026-08-04T14:16:32.693Z. Users of stunnel services, particularly those with network-accessible instances, should be aware of this vulnerability. Limited source details are available; defenders should verify affected deployments, review vendor guidance, and implement compensating controls. Evidence primarily indicates a stack-based out-of-bounds read vulnerability in stunnel's 's_vlog' function, and vendor remediation is recommended.
- Vendor
- stunnel
- Product
- stunnel
- CVSS
- MEDIUM 6.5
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-08-04
- Original CVE updated
- 2026-08-06
- Advisory published
- 2026-08-04
- Advisory updated
- 2026-08-06
Who should care
Users of stunnel services, particularly those with network-accessible stunnel instances, should be aware of this vulnerability and take defensive actions. Operators of affected platforms, vulnerability management teams, and security teams should review the vulnerability details and implement compensating controls where necessary. Asset owners with stunnel deployments should verify their exposure and plan for remediation or mitigation.
Technical summary
A stack-based out-of-bounds read vulnerability exists in stunnel's 's_vlog' function 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. The vulnerability could also be used to replace a series of trailing 'n' characters with '0' in certain corner cases.
Defensive priority
Medium-priority defensive actions are recommended due to the potential for service disruption.
Recommended defensive actions
- Apply vendor patches or updates for stunnel
- Implement network access controls to restrict access to stunnel services
- Monitor stunnel logs for oversized log messages
- Consider compensating controls such as intrusion detection systems
- Review stunnel configurations for exposure and assign owners for follow-up
- Track exceptions and retest remediated assets after verification
Evidence notes
Evidence is limited; primary official records indicate a stack-based out-of-bounds read vulnerability in stunnel's 's_vlog' function. Vendor remediation and compensating controls are recommended. The vulnerability allows remote attackers with network access to stunnel services to send protocol inputs triggering log messages longer than 1024 bytes, potentially leading to a crash. Limited source details are available, so defenders should verify affected stunnel deployments, review vendor guidance, and implement compensating controls.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-08-04T14:16:32.693Z and has not been modified since then.