Red Hat Security Advisory: openssl security update

Moderate

Multiple flaws were found in the way OpenSSL parsed X.509 certificates. An attacker could use these flaws to modify an X.509 certificate to produce a certificate with a different fingerprint without invalidating its signature, and possibly bypass fingerprint-based blacklisting in applications.

It was discovered that OpenSSL would accept ephemeral RSA keys when using non-export RSA cipher suites. A malicious server could make a TLS/SSL client using OpenSSL use a weaker key exchange method.

CWE-1240 - Use of a Cryptographic Primitive with a Risky Implementation

An out-of-bounds write flaw was found in the way OpenSSL reused certain ASN.1 structures. A remote attacker could possibly use a specially crafted ASN.1 structure that, when parsed by an application, would cause that application to crash.

CWE-787 - Out-of-bounds Write

A NULL pointer dereference flaw was found in OpenSSL's X.509 certificate handling implementation. A specially crafted X.509 certificate could cause an application using OpenSSL to crash if the application attempted to convert the certificate to a certificate request.

CWE-476 - NULL Pointer Dereference

A NULL pointer dereference was found in the way OpenSSL handled certain PKCS#7 inputs. An attacker able to make an application using OpenSSL verify, decrypt, or parse a specially crafted PKCS#7 input could cause that application to crash. TLS/SSL clients and servers using OpenSSL were not affected by this flaw.

CWE-476 - NULL Pointer Dereference

An integer underflow flaw, leading to a buffer overflow, was found in the way OpenSSL decoded malformed Base64-encoded inputs. An attacker able to make an application using OpenSSL decode a specially crafted Base64-encoded input (such as a PEM file) could use this flaw to cause the application to crash. Note: this flaw is not exploitable via the TLS/SSL protocol because the data being transferred is not Base64-encoded.

CWE-191 - Integer Underflow (Wrap or Wraparound)

A denial of service flaw was found in the way OpenSSL handled SSLv2 handshake messages. A remote attacker could use this flaw to cause a TLS/SSL server using OpenSSL to exit on a failed assertion if it had both the SSLv2 protocol and EXPORT-grade cipher suites enabled.

CWE-617 - Reachable Assertion

It was discovered that the SSLv2 servers using OpenSSL accepted SSLv2 connection handshakes that indicated non-zero clear key length for non-export cipher suites. An attacker could use this flaw to decrypt recorded SSLv2 sessions with the server by using it as a decryption oracle.

It was discovered that the SSLv2 protocol implementation in OpenSSL did not properly implement the Bleichenbacher protection for export cipher suites. An attacker could use a SSLv2 server using OpenSSL as a Bleichenbacher oracle.