CVE-2021-23840
7.5 · HIGHOverview
CVE-2021-23840 is a high-severity vulnerability affecting openssl openssl. It was published on February 16, 2021 and has a CVSS 3.1 base score of 7.5 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
Calls to EVP_CipherUpdate, EVP_EncryptUpdate and EVP_DecryptUpdate may overflow the output length argument in some cases where the input length is close to the maximum permissable length for an integer on the platform. In such cases the return value from the function call will be 1 (indicating success), but the output length value will be negative. This could cause applications to behave incorrectly or crash. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x).
Remediation
Check the references section for vendor advisories and patches from openssl. Update openssl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| openssl | openssl | >= 1.0.2, < 1.0.2y | Affected |
| tenable | log_correlation_engine | >= 0, < 6.0.8 | Affected |
| oracle | jd_edwards_enterpriseone_tools | >= 0, < 9.2.6.0 | Affected |
| oracle | mysql_server | >= 0, < 5.7.33 | Affected |
| oracle | nosql_database | >= 0, < 20.3 | Affected |
| mcafee | epolicy_orchestrator | >= 0, < 5.10.0 | Affected |
| fujitsu | m10-1_firmware | >= 0, < xcp2410 | Affected |
| fujitsu | m10-4_firmware | >= 0, < xcp2410 | Affected |
| fujitsu | m10-4s_firmware | >= 0, < xcp2410 | Affected |
References
Frequently Asked Questions
What is CVE-2021-23840?
CVE-2021-23840 is a high-severity vulnerability affecting openssl openssl. It was published on February 16, 2021 and has a CVSS 3.1 base score of 7.5 (HIGH).
How severe is CVE-2021-23840?
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2021-23840?
Check the references section for vendor advisories and patches from openssl. Update openssl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-23840?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-23840 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
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Browser-based exploitation validates findings with real proof-of-concept.
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