[OpenVPN-NL] Security advisory: mbed TLS CVE-2018-0497 and CVE-2018-0498

Steffan Karger steffan.karger at fox-it.com
Mon Aug 13 17:36:02 CEST 2018


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Summary:

OpenVPN-NL is not vulnerable to the two 'high'-rated security issues in
the recently published mbed TLS security advisory [0].


Background:

Recently, mbed TLS issued new software versions accompanied by a
security advisory containing two 'high'-rated security issues:

1) Remote plaintext recovery on use of CBC-based cipher suites through a
timing side-channel

Researchers showed that the mitigations for the lucky13 attack
implemented by mbedtls were not working properly for cipher suites using
SHA384 (or SHA512, but those do not exist).  This attack applies only
when using a TLS cipher suite that combines AES-CBC with SHA384.
OpenVPN-NL does not support such a cipher suite, and is therefor not
vulnerable.

2) Plaintext recovery on use of CBC-based cipher suites through a cache
based side-channel

Similar to the above, the implementation of the same cipher suites was
also vulnerable to cache-based side-channel attacks.  OpenVPN-NL does
not support any of the affected cipher suites, and is therefor not
vulnerable.


[0]
https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-a
dvisory-2018-02
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