CVE-2013-1623: Medium severity yaSSL CyaSSL vulnerability
A flaw in how TLS/DTLS, when CBC-mode encryption is used, communicates was reported. This vulnerability can allow for a Man-in-the-Middle attacker to recover plaintext from a TLS/DTLS connection, when CBC-mode encryption is used.
This flaw is in the TLS specification, and not a bug in a specific implementation (as such, it affects nearly all implementations). As such, it affects all TLS and DTLS implementations that are compliant with TLS 1.1 or 1.2, or with DTLS 1.0 or 1.2. It also applies to implementations of SSL 3.0 and TLS 1.0 that incorporate countermeasures to deal with previous padding oracle attacks. All TLS/DTLS ciphersuites that include CBC-mode encryption are potentially vulnerable.
The paper indicates that with OpenSSL, a full plaintext recovery attack is possible, and with GnuTLS, a partial plaintext recovery is possible (recovering up to 4 bits of the last byte in any block of plaintext).
To perform a successful attack, when TLS is used, a large number of TLS sessions are required (target plaintext must be sent repeatedly in the same position in the plaintext stream across the sessions). For DTLS, a successful attack can be carried out in a single session. The attacker must also be located close to the machine being attacked.
Further details are noted in the paper.
External References:
http://www.isg.rhul.ac.uk/tls/ http://www.isg.rhul.ac.uk/tls/TLStiming.pdf
Other sources
The TLS and DTLS implementations in wolfSSL CyaSSL before 2.5.0 do not properly consider timing side-channel attacks on a noncompliant MAC check operation during the processing of malformed CBC padding, which allows remote attackers to conduct distinguishing attacks and plaintext-recovery attacks via statistical analysis of timing data for crafted packets, a related issue to CVE-2013-0169.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2013-1623?
CVE-2013-1623 is considered to have a high severity due to its potential to allow a Man-in-the-Middle attack.
How do I fix CVE-2013-1623?
To remediate CVE-2013-1623, upgrade yaSSL to a version that addresses this vulnerability.
What systems are affected by CVE-2013-1623?
CVE-2013-1623 affects various versions of yaSSL, including multiple version numbers up to 2.4.6.
What type of attack does CVE-2013-1623 enable?
CVE-2013-1623 enables a Man-in-the-Middle attack allowing recovery of plaintext data from a TLS/DTLS connection.
Is CVE-2013-1623 a client-side or server-side vulnerability?
CVE-2013-1623 can be exploited on both the client-side and the server-side due to how TLS/DTLS is implemented.