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TLS Oracle Attack Vulnerabilities

Security researchers have released details of several RSA encryption vulnerabilities in the Transport Layer Security (TLS) protocol. They claim these vulnerabilities could be exploited to perform Bleichenbacher-style oracle attacks.

Threat ID:
CC-2926
Category:
Threat Severity:
Medium
Threat Vector:
Published:
13 February 2019 12:00 AM
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Summary

Security researchers have released details of several RSA encryption vulnerabilities in the Transport Layer Security (TLS) protocol. They claim these vulnerabilities could be exploited to perform Bleichenbacher-style oracle attacks.

Threat details

The vulnerabilities lie in the most common RSA configuration used by TLS, RSA Public-Key Cryptography Standard #1 (RSA-PKCS#1) version 1.5 (IETF RFC2313). The researchers discovered that this configuration may store information in exposed caches which can be obtained through side-channel attacks performed by privileged, local users. This information can then be used to implement a suitable padding oracle to decrypt or sign messages. Using this, the researchers found they were able to obtain the full 2048-bit RSA plaintext along with the premaster secret key in under 30 seconds.

The latest version of TLS, 1.3, was found to not be vulnerable by the researchers, although they were able to demonstrate several proof-of-concept methods for forcing TLS to downgrade to 1.2.

For further information:

Remediation steps

Type Step

Almost all affected TLS libraries have been updated to address these vulnerabilities. Users and administrators are encouraged to contact their relevant suppliers and ensure these updates are applied immediately.

Last edited: 14 February 2020 2:50 pm