-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 OpenSSL Security Advisory [09 September 2020] ============================================= Raccoon Attack (CVE-2020-1968) ============================== Severity: Low The Raccoon attack exploits a flaw in the TLS specification which can lead to an attacker being able to compute the pre-master secret in connections which have used a Diffie-Hellman (DH) based ciphersuite. In such a case this would result in the attacker being able to eavesdrop on all encrypted communications sent over that TLS connection. The attack can only be exploited if an implementation re-uses a DH secret across multiple TLS connections. Note that this issue only impacts DH ciphersuites and not ECDH ciphersuites. OpenSSL 1.1.1 is not vulnerable to this issue: it never reuses a DH secret and does not implement any "static" DH ciphersuites. OpenSSL 1.0.2f and above will only reuse a DH secret if a "static" DH ciphersuite is used. These static "DH" ciphersuites are ones that start with the text "DH-" (for example "DH-RSA-AES256-SHA"). The standard IANA names for these ciphersuites all start with "TLS_DH_" but excludes those that start with "TLS_DH_anon_". OpenSSL 1.0.2e and below would reuse the DH secret across multiple TLS connections in server processes unless the SSL_OP_SINGLE_DH_USE option was explicitly configured. Therefore all ciphersuites that use DH in servers (including ephemeral DH) are vulnerable in these versions. In OpenSSL 1.0.2f SSL_OP_SINGLE_DH_USE was made the default and it could not be turned off as a response to CVE-2016-0701. Since the vulnerability lies in the TLS specification, fixing the affected ciphersuites is not viable. For this reason 1.0.2w moves the affected ciphersuites into the "weak-ssl-ciphers" list. Support for the "weak-ssl-ciphers" is not compiled in by default. This is unlikely to cause interoperability problems in most cases since use of these ciphersuites is rare. Support for the "weak-ssl-ciphers" can be added back by configuring OpenSSL at compile time with the "enable-weak-ssl-ciphers" option. This is not recommended. OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2w. If upgrading is not viable then users of OpenSSL 1.0.2v or below should ensure that affected ciphersuites are disabled through runtime configuration. Also note that the affected ciphersuites are only available on the server side if a DH certificate has been configured. These certificates are very rarely used and for this reason this issue has been classified as LOW severity. This issue was found by Robert Merget, Marcus Brinkmann, Nimrod Aviram and Juraj Somorovsky and reported to OpenSSL on 28th May 2020 under embargo in order to allow co-ordinated disclosure with other implementations. Note ==== OpenSSL 1.0.2 is out of support and no longer receiving public updates. Extended support is available for premium support customers: https://www.openssl.org/support/contracts.html OpenSSL 1.1.0 is out of support and no longer receiving updates of any kind. The impact of this issue on OpenSSL 1.1.0 has not been analysed. Users of these versions should upgrade to OpenSSL 1.1.1. References ========== URL for this Security Advisory: https://www.openssl.org/news/secadv/20200909.txt Note: the online version of the advisory may be updated with additional details over time. For details of OpenSSL severity classifications please see: https://www.openssl.org/policies/secpolicy.html -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEeVOsH7w9yLOykjk+1enkP3357owFAl9YzBsACgkQ1enkP335 7oyIxg/9FWuca3/s/lY6g6a5VTPIekZMOLRUnDyzS3YePQu/sEd1w81mKoTqU+6F KQmliGqdRDk+KN8HDVd14kcLBukto8UKmkp9FpB5J4d2KK1I/Fg/DofJs6xUQYKb 5rHRLB3DDoyHEBzEEIjcqYTTThXW9ZSByVK9SKpC78IRM/B2dfd0+j4hIB/kDC/E G+wieFzexHQVdleVYT/VaJ6qS8AwvohBbt8h7yK0P6v/4vEm0spDbUmjWJBVUlUu QZyELjj8XZR3YFxt3axSuJg3JSGYlaMzkt2+DVq4qEzeJLIydLK9J8p6RNwPhsJk Rx0ez8P4N+5O7XmA0nHv3HyompdMgHlvykj8Ks4lNHVS02KKLi1jDtmOxl3Fm/hb ZNOmjn7lulV1342pw4rWL3Nge3x0s0Q5zgBCm1mqLzzu/V1ksx8FJwGA1w2cH280 dU9VedkC2wvFQije8pFrWH9l6N9Bh41DIEOnlBl0AL7IrbPdO6yMcD6vpR7hWjr3 fx4hNJSAGzJ3i/NXlSj4eR/47zkjfJyEc8Drc2QgewyqXFrK20X/LOj8MqJlc+ry pXZseh+XC8WaYDMV1ltrKvE2Ld9/0f3Ydc04AcDeu5SXPJG79ogzVnchZok7+XCj RT+a3/ES45+CTfL5v27t5QJxJcxg4siLVsILfi0rIUv0IYgH2fU= =U7OO -----END PGP SIGNATURE-----
