CVE-2023-3817 Excessive time spent checking DH q parameter value

What is CVE-2023-3817?

CVE-2023-3817 is a medium-severity denial of service vulnerability in Openssl Openssl, published on 31 Jul 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-834, CWE-606

Which versions are affected by CVE-2023-3817?

It affects 1 product.

Products include Openssl Openssl.

How do I fix CVE-2023-3817?

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-2023-3817 being exploited?

There is no known exploitation of CVE-2023-3817 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-2023-3817, AZL-27815, AZL-27817, AZL-31139, AZL-34669, AZL-35247 and 26 more.