CVE-2023-3817 OpenSSL CVE debrief

Who should care

Organizations operating Siemens SINEC INS industrial network management systems, developers of applications using OpenSSL for DH parameter validation, operators of services that process externally-provided cryptographic parameters, and security teams responsible for industrial control system infrastructure should prioritize assessment and remediation.

Technical summary

The vulnerability exists in OpenSSL's DH parameter validation logic where the `DH_check()` function and its variants perform unnecessary and computationally expensive checks when the `q` parameter exceeds the modulus `p`. This occurs because the validation routines do not short-circuit checks that are mathematically impossible to satisfy. The affected code paths include `DH_check()`, `DH_check_ex()`, `EVP_PKEY_param_check()`, and downstream consumers including `dhparam` and `pkeyparam` utilities with the `-check` flag. The root cause is a missing bounds check that would skip validation when `q > p`, which is always invalid for correct DH parameters. Attackers can exploit this by supplying crafted DH parameters with artificially inflated `q` values to applications that perform validation on untrusted input, causing excessive CPU consumption and service degradation.

Defensive priority

medium

Recommended defensive actions

• Apply vendor-provided updates: Siemens SINEC INS users should update to V1.0 SP2 Update 3 or later version
• Review applications utilizing OpenSSL DH_check(), DH_check_ex(), or EVP_PKEY_param_check() functions for validation of externally-sourced DH parameters
• Implement input validation to reject DH parameters with q values exceeding the modulus p before passing to OpenSSL validation functions
• Monitor for anomalous resource consumption patterns in services performing cryptographic parameter validation
• Assess exposure of command-line utilities dhparam and pkeyparam with -check option to untrusted input sources
• Consider network segmentation to limit exposure of affected services to untrusted networks
• Review CISA ICS recommended practices for defense-in-depth strategies applicable to industrial control systems

Evidence notes

The vulnerability description is sourced from CISA CSAF advisory ICSA-24-319-08, which references Siemens security advisory SSA-915275. The issue was discovered as a follow-up to CVE-2023-3446 remediation. The CVSS 3.1 vector indicates network attack vector, low attack complexity, no privileges required, no user interaction, unchanged scope, with low availability impact.

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.