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CVE-2019-6593 mitigations besides disabling CBC

Question asked by mreavey on Jun 20, 2019
Latest reply on Jun 24, 2019 by mreavey

Good morning folks,

 

Clearly disabling CBC ciphers is the recommendation I am reading when looking around for mitigations for the new variants. For some sites I am getting an F and the only way I have been able to get the A is to disable the CBC ciphers. I got that, but the obvious problem is IE11 and Windows 7 support for client base.

 

However, when I test a few sites in the cloud, including our own and some very popular ones, they are still getting an A despite still having the CBC in their cipher suites. How can we have it both ways too?

 

Is there something about IaaS and PaaS services or containerization that mitigates this? Trying to understand what a chosen-cipher attack is and how a cloud service or deployment model would matter to obtaining the private key may be irrelevant.

 

I just want to know how they are getting the A while still supporting these CBC ciphers in their suites:

 

e.g. Amazon.com

https://www.ssllabs.com/ssltest/analyze.html?d=amazon.com&s=176.32.98.166&hideResults=on&latest

 

e.g. Chase.com

https://www.ssllabs.com/ssltest/analyze.html?d=chase.com&s=159.53.224.21&hideResults=on&latest

 

 

sslscan --no-injection chase.com

Version: 1.11.13-static

OpenSSL 1.0.2f  28 Jan 2016

 

Connected to 159.53.84.126

 

Testing SSL server chase.com on port 443 using SNI name chase.com

 

  TLS Fallback SCSV:

Server supports TLS Fallback SCSV

 

  TLS renegotiation:

Secure session renegotiation supported

 

  TLS Compression:

Compression disabled

 

  Heartbleed:

TLS 1.2 not vulnerable to heartbleed

TLS 1.1 not vulnerable to heartbleed

TLS 1.0 not vulnerable to heartbleed

 

  Supported Server Cipher(s):

Preferred TLSv1.2  128 bits  ECDHE-RSA-AES128-GCM-SHA256  Curve P-256 DHE 256

Accepted  TLSv1.2  256 bits  ECDHE-RSA-AES256-GCM-SHA384  Curve P-256 DHE 256

Accepted  TLSv1.2  128 bits  ECDHE-RSA-AES128-SHA256       Curve P-256 DHE 256

Accepted  TLSv1.2  256 bits  ECDHE-RSA-AES256-SHA384       Curve P-256 DHE 256

Accepted  TLSv1.2  128 bits  ECDHE-RSA-AES128-SHA          Curve P-256 DHE 256

Accepted  TLSv1.2  256 bits  ECDHE-RSA-AES256-SHA          Curve P-256 DHE 256

Accepted  TLSv1.2  128 bits  AES128-GCM-SHA256            

Accepted  TLSv1.2  256 bits  AES256-GCM-SHA384            

Accepted  TLSv1.2  128 bits  AES128-SHA256                

Accepted  TLSv1.2  256 bits  AES256-SHA256                

Accepted  TLSv1.2  128 bits  AES128-SHA                   

Accepted  TLSv1.2  256 bits  AES256-SHA                   

Preferred TLSv1.1  128 bits  ECDHE-RSA-AES128-SHA          Curve P-256 DHE 256

Accepted  TLSv1.1  256 bits  ECDHE-RSA-AES256-SHA          Curve P-256 DHE 256

Accepted  TLSv1.1  128 bits  AES128-SHA                   

Accepted  TLSv1.1  256 bits  AES256-SHA                   

Preferred TLSv1.0  128 bits  ECDHE-RSA-AES128-SHA          Curve P-256 DHE 256

Accepted  TLSv1.0  256 bits  ECDHE-RSA-AES256-SHA          Curve P-256 DHE 256

Accepted  TLSv1.0  128 bits  AES128-SHA                   

Accepted  TLSv1.0  256 bits  AES256-SHA                   

 

  SSL Certificate:

Signature Algorithm: sha256WithRSAEncryption

RSA Key Strength:    2048

 

Subject:  www.chase.com

Altnames: DNS:www.chase.com, DNS:chase.com

Issuer:   Entrust Certification Authority - L1M

 

Not valid before: Mar 21 12:17:35 2019 GMT

Not valid after:  Mar 21 12:47:35 2020 GMT

 

 

 

I am not finding anything online offering any explanation as to why they get the A while still supporting those ciphers. This could also be that I do not understand something fundamental here. Any insight is appreciated.

 

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