OpenSSL contains a vulnerability that could an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to improper handling of Online Certificate Status Protocol (OCSP) response verification messages. An unauthenticated, remote attacker could exploit the vulnerability by transmitting a crafted certificate response with an invalid key. Successful exploitation could allow an attacker to cause a DoS condition on the targeted system.
OpenSSL has confirmed the vulnerability and released software updates.
Indicators of Compromise
The following OpenSSL versions are vulnerable:
1.0.1c and prior
1.0.0j and prior
0.9.8x and prior
The vulnerability is due to insufficient checks for NULL keys implemented in the OpenSSL source code files crypto/ocsp/ocsp_vfy.c and crypto/asn1/a_verify.c when handling OCSP signatures.
An unauthenticated, remote attacker could exploit the vulnerability by hosting a malicious OCSP server and responding to OCSP verifications with a crafted OCSP certificate response that contains a NULL key. When the malicious response is processed by the affected software, the software could terminate abnormally, denying service to legitimate users. Successful exploitation could allow an attacker to cause a DoS condition on the targeted system.
To exploit the vulnerability, the attacker may need access to trusted or internal networks to send crafted messages to the targeted system. This access requirement could limit the likelihood of a successful exploit.
Administrators are advised to apply the appropriate updates.
Administrators may consider using an alternate product.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
OpenSSL has released a security advisory at the following link: secadv_20130204
Apple has released a security advisory at the following link: HT5880
Oracle customers are advised to acquire the Solaris 9 and 10 updates via normal Oracle support channels.
Red Hat has released updated software for registered subscribers at the following link: Red Hat Network. Red Hat packages can be updated on Red Hat Enterprise Linux versions 5 and later using the yum tool.
Red Hat has released updated packages for registered users at the following links:
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.