CVE-2021-23839
3.7 · LOWOverview
CVE-2021-23839 is a low-severity vulnerability affecting openssl openssl. It was published on February 16, 2021 and has a CVSS 3.1 base score of 3.7 (LOW).
This vulnerability has a CVSS 3.1 base score of 3.7, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
OpenSSL 1.0.2 supports SSLv2. If a client attempts to negotiate SSLv2 with a server that is configured to support both SSLv2 and more recent SSL and TLS versions then a check is made for a version rollback attack when unpadding an RSA signature. Clients that support SSL or TLS versions greater than SSLv2 are supposed to use a special form of padding. A server that supports greater than SSLv2 is supposed to reject connection attempts from a client where this special form of padding is present, because this indicates that a version rollback has occurred (i.e. both client and server support greater than SSLv2, and yet this is the version that is being requested). The implementation of this padding check inverted the logic so that the connection attempt is accepted if the padding is present, and rejected if it is absent. This means that such as server will accept a connection if a version rollback attack has occurred. Further the server will erroneously reject a connection if a normal SSLv
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 | 1.0.2s | Affected |
| siemens | sinec_ins | >= 0, < 1.0 | Affected |
References
Frequently Asked Questions
What is CVE-2021-23839?
CVE-2021-23839 is a low-severity vulnerability affecting openssl openssl. It was published on February 16, 2021 and has a CVSS 3.1 base score of 3.7 (LOW).
How severe is CVE-2021-23839?
This vulnerability has a CVSS 3.1 base score of 3.7, rated LOW. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2021-23839?
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-2021-23839?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-23839 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.
AI-driven PR review catches vulnerable dependencies before they ship.
Browser-based exploitation validates findings with real proof-of-concept.
Related LOW CVEs from 2021
View all →ide_atapi_cmd_reply_end in hw/ide/atapi.c in QEMU 5.1.0 allows out-of-bounds read access because a b
The ownCloud application before 2.15 for Android allows attackers to use adb to include a PIN prefer
fr-archive-libarchive.c in GNOME file-roller through 3.38.0, as used by GNOME Shell and other softwa
Vulnerability in the Hyperion Financial Management product of Oracle Hyperion (component: Task Autom
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex TCM 4351B inst
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Nextcloud Android app is the Android client for Nextcloud. In versions prior to 3.16.1, a malicious
Trusty TLK contains a vulnerability in its access permission settings where it does not properly res