CVE-2021-23841 Explained : Impact and Mitigation
Learn about CVE-2021-23841, a vulnerability in OpenSSL's X509_issuer_and_serial_hash() function that can lead to denial of service attacks. Find out affected versions and recommended mitigation steps.
A vulnerability in OpenSSL, tracked as CVE-2021-23841, could lead to a denial of service attack due to a NULL pointer dereference issue in the X509_issuer_and_serial_hash() function.
Understanding CVE-2021-23841
This CVE ID refers to a security flaw in OpenSSL that poses a risk to systems using specific vulnerable versions of the software.
What is CVE-2021-23841?
The OpenSSL function X509_issuer_and_serial_hash() creates a unique hash value but mishandles potential errors in the issuer field parsing, allowing a NULL pointer dereference, leading to a crash and potential denial of service.
The Impact of CVE-2021-23841
The vulnerability affects OpenSSL versions 1.1.1i and below, as well as versions 1.0.2x and below. Users should upgrade to OpenSSL 1.1.1j or 1.0.2y depending on the version in use to mitigate the risk.
Technical Details of CVE-2021-23841
The vulnerability arises from errors in parsing the issuer field of X509 certificates, triggering a NULL pointer dereference and subsequent denial of service risk.
Vulnerability Description
The issue stems from the X509_issuer_and_serial_hash() function's failure to handle errors correctly while processing the issuer field, creating a potential crash scenario.
Affected Systems and Versions
OpenSSL versions 1.1.1i and below, as well as versions 1.0.2x and below, are vulnerable. Users should upgrade to specified fixed versions to address the issue.
Exploitation Mechanism
Applications directly calling the vulnerable function on untrusted certificates obtained from external sources are at risk of exploitation, potentially leading to a denial of service attack.
Mitigation and Prevention
To address the CVE-2021-23841 vulnerability, immediate actions include upgrading OpenSSL to the patched versions and adopting secure practices for long-term security.
Immediate Steps to Take
Users of affected versions should promptly update OpenSSL to versions 1.1.1j or 1.0.2y as per the specific affected release to eliminate the risk of exploitation.
Long-Term Security Practices
In addition to patching OpenSSL, implement secure certificate handling practices within applications to prevent similar vulnerabilities from being exploited in the future.
Patching and Updates
Regularly check for security updates from OpenSSL and apply patches promptly to address known vulnerabilities and enhance system security.