Vulnerability Database

328,409

Total vulnerabilities in the database

CVE-2023-3817

Issue summary: Checking excessively long DH keys or parameters may be very slow.

Impact summary: Applications that use the functions DH_check(), DH_check_ex() or EVP_PKEY_param_check() to check a DH key or DH parameters may experience long delays. Where the key or parameters that are being checked have been obtained from an untrusted source this may lead to a Denial of Service.

The function DH_check() performs various checks on DH parameters. After fixing CVE-2023-3446 it was discovered that a large q parameter value can also trigger an overly long computation during some of these checks. A correct q value, if present, cannot be larger than the modulus p parameter, thus it is unnecessary to perform these checks if q is larger than p.

An application that calls DH_check() and supplies a key or parameters obtained from an untrusted source could be vulnerable to a Denial of Service attack.

The function DH_check() is itself called by a number of other OpenSSL functions. An application calling any of those other functions may similarly be affected. The other functions affected by this are DH_check_ex() and EVP_PKEY_param_check().

Also vulnerable are the OpenSSL dhparam and pkeyparam command line applications when using the "-check" option.

The OpenSSL SSL/TLS implementation is not affected by this issue.

The OpenSSL 3.0 and 3.1 FIPS providers are not affected by this issue.

  • Published: Jul 31, 2023
  • Updated: Nov 16, 2025
  • CVE: CVE-2023-3817
  • Severity: Medium
  • Exploit:

CVSS v3:

  • Severity: Medium
  • Score: 5.3
  • AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Software From Fixed in
openssl / openssl 1.0.2a 1.0.2a.x
openssl / openssl 1.0.2e 1.0.2e.x
openssl / openssl 1.0.2j 1.0.2j.x
openssl / openssl 1.0.2b 1.0.2b.x
openssl / openssl 1.0.2g 1.0.2g.x
openssl / openssl 1.0.2h 1.0.2h.x
openssl / openssl 1.0.2c 1.0.2c.x
openssl / openssl 1.0.2-beta3 1.0.2-beta3.x
openssl / openssl 1.0.2-beta1 1.0.2-beta1.x
openssl / openssl 1.0.2f 1.0.2f.x
openssl / openssl 1.0.2-beta2 1.0.2-beta2.x
openssl / openssl 1.0.2i 1.0.2i.x
openssl / openssl 1.0.2d 1.0.2d.x
openssl / openssl 1.0.2k 1.0.2k.x
openssl / openssl 1.0.2l 1.0.2l.x
openssl / openssl 1.0.2m 1.0.2m.x
openssl / openssl 1.0.2zb 1.0.2zb.x
openssl / openssl 1.0.2 1.0.2.x
openssl / openssl 1.0.2n 1.0.2n.x
openssl / openssl 1.0.2o 1.0.2o.x
openssl / openssl 1.0.2p 1.0.2p.x
openssl / openssl 1.0.2q 1.0.2q.x
openssl / openssl 1.0.2r 1.0.2r.x
openssl / openssl 1.0.2s 1.0.2s.x
openssl / openssl 1.0.2t 1.0.2t.x
openssl / openssl 1.0.2u 1.0.2u.x
openssl / openssl 1.0.2v 1.0.2v.x
openssl / openssl 1.0.2w 1.0.2w.x
openssl / openssl 1.0.2x 1.0.2x.x
openssl / openssl 1.0.2y 1.0.2y.x
openssl / openssl 1.0.2za 1.0.2za.x
openssl / openssl 1.1.1 1.1.1.x
openssl / openssl 1.1.1-pre1 1.1.1-pre1.x
openssl / openssl 1.1.1-pre2 1.1.1-pre2.x
openssl / openssl 1.1.1-pre3 1.1.1-pre3.x
openssl / openssl 1.1.1-pre4 1.1.1-pre4.x
openssl / openssl 1.1.1-pre5 1.1.1-pre5.x
openssl / openssl 1.1.1-pre6 1.1.1-pre6.x
openssl / openssl 1.1.1-pre7 1.1.1-pre7.x
openssl / openssl 1.1.1-pre8 1.1.1-pre8.x
openssl / openssl 1.1.1-pre9 1.1.1-pre9.x
openssl / openssl 1.1.1a 1.1.1a.x
openssl / openssl 1.1.1b 1.1.1b.x
openssl / openssl 1.1.1c 1.1.1c.x
openssl / openssl 1.1.1d 1.1.1d.x
openssl / openssl 1.1.1e 1.1.1e.x
openssl / openssl 1.1.1f 1.1.1f.x
openssl / openssl 1.1.1g 1.1.1g.x
openssl / openssl 1.1.1h 1.1.1h.x
openssl / openssl 1.1.1i 1.1.1i.x
openssl / openssl 1.1.1j 1.1.1j.x
openssl / openssl 1.1.1k 1.1.1k.x
openssl / openssl 1.1.1l 1.1.1l.x
openssl / openssl 3.1.0 3.1.2
openssl / openssl 3.0.0 3.0.10
openssl / openssl 1.1.1m 1.1.1m.x
openssl / openssl 1.1.1n 1.1.1n.x
openssl / openssl 1.1.1o 1.1.1o.x
openssl / openssl 1.1.1p 1.1.1p.x
openssl / openssl 1.1.1q 1.1.1q.x
openssl / openssl 1.1.1r 1.1.1r.x
openssl / openssl 1.1.1s 1.1.1s.x
openssl / openssl 1.1.1t 1.1.1t.x
openssl / openssl 1.1.1u 1.1.1u.x
openssl / openssl 1.0.2zc 1.0.2zc.x
openssl / openssl 1.0.2zd 1.0.2zd.x
openssl / openssl 1.0.2ze 1.0.2ze.x
openssl / openssl 1.0.2zf 1.0.2zf.x
openssl / openssl 1.0.2zg 1.0.2zg.x
openssl / openssl 1.0.2zh 1.0.2zh.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.