The announcement claims that this affects SSL_check_chain(). Is that an exhaustive list? If an application does NOT call that function, does this mean the vulnerability is not exploitable? I ask because the the fixed function tls1_check_sig_alg is called by tls1_check_chain, and that is called directly by SSL_check_chain, but it is also called by tls1_set_cert_validity, and that is called from inside the tls state machine, but with different parameters, so its a bit hard to see if it is affected or not. Thanks, Sam On Tue, Apr 21, 2020 at 6:26 AM OpenSSL <openssl@xxxxxxxxxxx> wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA256 > > OpenSSL Security Advisory [21 April 2020] > ========================================= > > Segmentation fault in SSL_check_chain (CVE-2020-1967) > ===================================================== > > Severity: High > > Server or client applications that call the SSL_check_chain() function during or > after a TLS 1.3 handshake may crash due to a NULL pointer dereference as a > result of incorrect handling of the "signature_algorithms_cert" TLS extension. > The crash occurs if an invalid or unrecognised signature algorithm is received > from the peer. This could be exploited by a malicious peer in a Denial of > Service attack. > > OpenSSL version 1.1.1d, 1.1.1e, and 1.1.1f are affected by this issue. This > issue did not affect OpenSSL versions prior to 1.1.1d. > > Affected OpenSSL 1.1.1 users should upgrade to 1.1.1g > > This issue was found by Bernd Edlinger and reported to OpenSSL on 7th April > 2020. It was found using the new static analysis pass being implemented in GCC, > - -fanalyzer. Additional analysis was performed by Matt Caswell and Benjamin > Kaduk. > > Note > ===== > > This issue did not affect OpenSSL 1.0.2 however these versions are out of > support and no longer receiving public updates. Extended support is available > for premium support customers: https://www.openssl.org/support/contracts.html > > This issue did not affect OpenSSL 1.1.0 however these versions are out of > support and no longer receiving updates. > > Users of these versions should upgrade to OpenSSL 1.1.1. > > References > ========== > > URL for this Security Advisory: > https://www.openssl.org/news/secadv/20200421.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----- > > iQEzBAEBCAAdFiEEhlersmDwVrHlGQg52cTSbQ5gRJEFAl6e8uwACgkQ2cTSbQ5g > RJHHRgf+J8iVBuK6EoOvf9xm9geiDgYVFse9ckMXH92gdGbwsW4uhTNk9fCyNC+t > vsf6YGT6nKJarB5+N+LC4QB7VLo/DjlYcN9zP3mubV0eEyKHSoW6tDOWPpJ0gsbt > 2Z9iTA4GnofvhBcWLiPGgv4IUHknsOaPkRmEppSF0fDTSKuYOerfNRh9jTKHulis > Ph6dCOXE3kb5HfMwVj3UN2sP92XTig4FzpIQaZ1/2jKZaRXtzJD7pvu1fDCTkUGl > aeta5jHNypYyRKJLuJ1+1DiBtbWTFAWMUCHlkg/kgdU4hIl/lo3vgAyFs/9mQxZQ > vj2rIjoJHRj0EXqXhHoABqBHedilJQ== > =AXyP > -----END PGP SIGNATURE-----
