CVE-2023-5678 Excessive time spent in DH check / generation with large Q parameter value

What is CVE-2023-5678?

CVE-2023-5678 is a medium-severity denial of service vulnerability in Openssl Openssl, published on 6 Nov 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Issue summary: Generating excessively long X9.42 DH keys or checking excessively long X9.42 DH keys or parameters may be very slow.

Impact summary: Applications that use the functions DH_generate_key() to generate an X9.42 DH key may experience long delays. Likewise, applications that use DH_check_pub_key(), DH_check_pub_key_ex() or EVP_PKEY_public_check() to check an X9.42 DH key or X9.42 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.

While DH_check() performs all the necessary checks (as of CVE-2023-3817), DH_check_pub_key() doesn't make any of these checks, and is therefore vulnerable for excessively large P and Q parameters.

Likewise, while DH_generate_key() performs a check for an excessively large P, it doesn't check for an excessively large Q.

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

DH_generate_key() and DH_check_pub_key() are also 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_pub_key_ex(), EVP_PKEY_public_check(), and EVP_PKEY_generate().

Also vulnerable are the OpenSSL pkey command line application when using the "-pubcheck" option, as well as the OpenSSL genpkey command line application.

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.

Weakness: CWE-754, CWE-606

Which versions are affected by CVE-2023-5678?

It affects 1 product.

Products include Openssl Openssl.

How do I fix CVE-2023-5678?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2023-5678 being exploited?

There is no known exploitation of CVE-2023-5678 in the wild and no public exploit code.

Other vulnerabilities in Openssl Openssl

• CVE-2009-3245 Null dereference in n/a Critical 10.0
• CVE-2006-3738 Memory corruption in n/a Critical 10.0
• CVE-2026-63073 Untrusted Sender DN Used as Format String in CMP Response Validation Critical 9.8
• CVE-2016-6309 Use after free in n/a Critical 9.8
• CVE-2016-0799 Integer overflow in n/a Critical 9.8

All Openssl Openssl vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2023-5678, AZL-31872, AZL-31880, AZL-34666, AZL-35084, AZL-37740 and 32 more.