CVE-2026-74994 Erlang CVE debrief

Who should care

Defenders responsible for OTP installations, particularly those using inets httpd server with multiple directory configuration blocks and dets or mnesia authentication backends, should assess exposure and prioritize remediation.

Why it matters

CVE-2026-74994 affects OTP's inets httpd server, allowing users added to one protected directory to be accepted as valid for all other protected directories on the same server instance. Defenders should prioritize verifying and upgrading affected OTP versions, ensuring proper configuration of authentication backends, and monitoring user access.

• User access across protected directories may be incorrectly validated
• Authentication backend configuration may need to be revised
• Monitoring and logging of user access may be required to detect potential misuse

Technical summary

The mod_auth module in OTP's inets httpd server, when configured with dets or mnesia authentication backends and multiple directory configuration blocks, collapses all directory blocks into a single shared user/group namespace. A user added to one protected directory is accepted as valid for all other protected directories on the same server instance. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown. The vulnerability allows users added to one  

Defensive priority

Defenders should prioritize verifying and upgrading affected OTP versions, ensuring proper configuration of authentication backends, and monitoring user access across protected directories.

Recommended defensive actions

• Verify and upgrade affected OTP versions to the latest security patch
• Ensure proper configuration of authentication backends and directory blocks
• Monitor user access and authentication across protected directories
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description, affected versions, and references to source-specific vulnerability assessments. The mod_auth module in OTP's inets httpd server, when configured with dets or mnesia authentication backends and multiple directory configuration blocks, collapses all directory blocks into a single shared user/group namespace. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, which  

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.