CVE-2023-6237 (CVSS 5.9)

Description

Issue summary: Checking excessively long invalid RSA public keys may take a long time. Impact summary: Applications that use the function EVP_PKEY_public_check() to check RSA public keys may experience long delays. Where the key that is being checked has been obtained from an untrusted source this may lead to a Denial of Service. When function EVP_PKEY_public_check() is called on RSA public keys, a computation is done to confirm that the RSA modulus, n, is composite. For valid RSA keys, n is a product of two or more large primes and this computation completes quickly. However, if n is an overly large prime, then this computation would take a long time. An application that calls EVP_PKEY_public_check() and supplies an RSA key obtained from an untrusted source could be vulnerable to a Denial of Service attack. The function EVP_PKEY_public_check() is not called from other OpenSSL functions however it is called from the OpenSSL pkey command line application. For that reason that application is also vulnerable if used with the '-pubin' and '-check' options on untrusted data. The OpenSSL SSL/TLS implementation is not affected by this issue. The OpenSSL 3.0 and 3.1 FIPS providers are affected by this issue.

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CVSS v3.1 Score

5.9

MEDIUM

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

Weakness Type (CWE)

CWE-606 CWE-606

References

Other References

https://github.com/openssl/openssl/commit/0b0f7abfb37350794a4b8960fafc292cd5d1b84d https://github.com/openssl/openssl/commit/18c02492138d1eb8b6548cb26e7b625fb2414a2a https://github.com/openssl/openssl/commit/a830f551557d3d66a84bbb18a5b889c640c36294 https://www.openssl.org/news/secadv/20240115.txt http://www.openwall.com/lists/oss-security/2024/03/11/1 https://github.com/openssl/openssl/commit/0b0f7abfb37350794a4b8960fafc292cd5d1b84d https://github.com/openssl/openssl/commit/18c02492138d1eb8b6548cb26e7b625fb2414a2a https://github.com/openssl/openssl/commit/a830f551557d3d66a84bbb18a5b889c640c36294 https://security.netapp.com/advisory/ntap-20240531-0007/ https://www.openssl.org/news/secadv/20240115.txt

Frequently Asked Questions

What is CVE-2023-6237? +

Issue summary: Checking excessively long invalid RSA public keys may take a long time. Impact summary: Applications that use the function EVP_PKEY_public_check() to check RSA public keys may experience long delays. Where the key that is being checked has been obtained from an untrusted source this may lead to a Denial of Service. When function EVP_PKEY_public_check() is called on RSA public keys, a computation is done to confirm that the RSA modulus, n, is composite. For valid RSA keys, n is a product of two or more large primes and this computation completes quickly. However, if n is an overly large prime, then this computation would take a long time. An application that calls EVP_PKEY_public_check() and supplies an RSA key obtained from an untrusted source could be vulnerable to a Denial of Service attack. The function EVP_PKEY_public_check() is not called from other OpenSSL functions however it is called from the OpenSSL pkey command line application. For that reason that application is also vulnerable if used with the '-pubin' and '-check' options on untrusted data. The OpenSSL SSL/TLS implementation is not affected by this issue. The OpenSSL 3.0 and 3.1 FIPS providers are affected by this issue. It has a CVSS v3.1 base score of 5.9 (MEDIUM).

How severe is CVE-2023-6237? +

CVE-2023-6237 has a CVSS v3.1 score of 5.9 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

How do I check if I'm vulnerable to CVE-2023-6237? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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