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_c...

Description

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.

Metrics

CVSS 3.1

5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS Probability

2.58%

83.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Openssl	Openssl	>= 3.0.0, < 3.0.10
Openssl	Openssl	>= 3.1.0, < 3.1.2
Openssl	Openssl	1.0.2
Openssl	Openssl	1.0.2a
Openssl	Openssl	1.0.2b
Openssl	Openssl	1.0.2c
Openssl	Openssl	1.0.2d
Openssl	Openssl	1.0.2e
Openssl	Openssl	1.0.2f
Openssl	Openssl	1.0.2g
Openssl	Openssl	1.0.2h
Openssl	Openssl	1.0.2i
Openssl	Openssl	1.0.2j
Openssl	Openssl	1.0.2k
Openssl	Openssl	1.0.2l
Openssl	Openssl	1.0.2m
Openssl	Openssl	1.0.2n
Openssl	Openssl	1.0.2o
Openssl	Openssl	1.0.2p
Openssl	Openssl	1.0.2q
Openssl	Openssl	1.0.2r
Openssl	Openssl	1.0.2s
Openssl	Openssl	1.0.2t
Openssl	Openssl	1.0.2u
Openssl	Openssl	1.0.2v
Openssl	Openssl	1.0.2w
Openssl	Openssl	1.0.2x
Openssl	Openssl	1.0.2y
Openssl	Openssl	1.0.2za
Openssl	Openssl	1.0.2zb
Openssl	Openssl	1.0.2zc
Openssl	Openssl	1.0.2zd
Openssl	Openssl	1.0.2ze
Openssl	Openssl	1.0.2zf
Openssl	Openssl	1.0.2zg
Openssl	Openssl	1.0.2zh
Openssl	Openssl	1.1.1
Openssl	Openssl	1.1.1a
Openssl	Openssl	1.1.1b
Openssl	Openssl	1.1.1c
Openssl	Openssl	1.1.1d
Openssl	Openssl	1.1.1e
Openssl	Openssl	1.1.1f
Openssl	Openssl	1.1.1g
Openssl	Openssl	1.1.1h
Openssl	Openssl	1.1.1i
Openssl	Openssl	1.1.1j
Openssl	Openssl	1.1.1k
Openssl	Openssl	1.1.1l
Openssl	Openssl	1.1.1m

Showing 50 of 58 affected configurations. See NVD for the full list.

References

Timeline

Published: Jul 31, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is 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.

How severe is CVE-2023-3817?

CVE-2023-3817 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 2.58% probability of exploitation in the next 30 days.

How do I fix CVE-2023-3817?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.