Firefox reporting "Your connection is not secure" for sites

I upgraded Firefox on a Linux system running CentOS 7 to version 52.8.0-1 with yum upgrade firefox. When I opened Firefox afterwards and put in the address bar, I saw the message below:

Your connection is not secure

The website tried to negotiate an inadequate level of security.

uses security technology that is outdated and vulnerable to attack. An attacker could easily reveal information which you thought to be safe. The website administrator will need to fix the server first before you can visit the site.


When I went to another site,, using HTTPS, I saw the same message. I checked to ensure that the web browser wasn't configured to use a proxy by clicking on the icon with the three horizontal bars at the top, right-hand side of the browser window and selecting Preferences, then Advanced, then Network, then Settings. The setting was "No proxy." I then right-clicked on the "Your connection is not secure" page and chose View Page Info. When I clicked on the Security tab, I saw the "Owner" value listed as "This website does not supply ownership information." In the Technical Details section, I saw "Connection Not Encrypted" and "The website does not support encryption for the page you are viewing," even though the URL listed was

Firefox - connection not 

I disabled the NoScript add-on and tried accessing, but saw the same message. I tried another web browser on the system, Vivaldi, but didn't see the issue within that browser. So I then opened Wireshark, a free and open-source software packet analyzer and captured the network traffic between the Google webserver and the CentOS host. When I attempted to access the Google server again, I saw a Domain Name System (DNS) query for the address of the server and the response from the DNS server, which indicated that the IP address was, which when I performed a reverse DNS lookup with the nslookup command equated to

# nslookup

Non-authoritative answer:	name =	name =

Authoritative answers can be found from:


The domain name is registered to Google - see What is 1e100 is scientific notation for 1 googol, i.e., 1 raised to the power of 100, which is 1 followed by one hundred zeros. Google uses the domain name for its servers. So there wasn't an issue with some intervening system providing the wrong IP address for the Google server.

I then checked the packets that followed the DNS response. I saw the expected three way handshake between the host and Google server, i.e., the host sent a SYN packet, the server responsded with a SYN, ACK packet, and then the host responded to the server's SYN request with its own ACK packet. I then saw a "Client Hello" packet sent from the browser on the client. The server sent an ACK back. Wireshark then showed a "Server Hello, Change Cipher Spec, Hello Request, Hello Request" packet being sent from the server to the client. The client system then sent a "Change Cipher Spec, Hello Request, Hello Request" packet and then an "Encrypted Alert" packet.

Wireshark - Encrypted Alert

That packet was followed immediately by a FIN, ACK packet from the client to the server. The server then sent Application Data in reply and the client reset the connection with a RST packet.

I thought, perhaps, that the system didn't currently support the latest version of the Transport Layer Security (TLS) protocol, but the protocol listed for the TLS packets by Wireshark was TLSv1.2. When I looked at the place where the TLS version number is referenced in the Secure Sockets Layer (SSL) section in the "Client Hello" packet, I saw that packet used TLS version 1.0 - Wireshark showed "TLS 1.0 (0x0301)" for the Version.

Client Hello TLS 1.0

The hexadecimal values for various versions of SSL/TLS are listed below:

Mastering Wireshark
Mastering Wireshark
1x1 px

VersionHexadecimal Value
SSL 3.00x0300
TLS 1.00x0301
TLS 1.10x0302
TLS 1.20x0303

But when I looked at the "Change Cipher Spec" packet subsequently sent by the client system, though, I saw it was using TLS version 1.2.

Wireshark - Change Cipher Spec TLS v1.2

And when I used the openssl utility to check the ciphers supported on the client system, I saw TLSv1.2 was supported.

$ openssl ciphers -v | awk '{print $2}' | sort | uniq

So I thought the issue probably was not caused by use of an outdated cipher on the client side. But, since I thought openssl was probably out-of-date, I updated it with yum upgrade openssl.

# openssl version
OpenSSL 1.0.1e-fips 11 Feb 2013
# yum upgrade openssl
Loading mirror speeds from cached hostfile
<text snipped>
Dependencies Resolved

 Package              Arch           Version                 Repository    Size
 openssl              x86_64         1:1.0.2k-12.el7         base         492 k
Updating for dependencies:
 openssl-libs         x86_64         1:1.0.2k-12.el7         base         1.2 M

Transaction Summary
Upgrade  1 Package (+1 Dependent package)

Total download size: 1.7 M
Is this ok [y/d/N]: y
Downloading packages:
No Presto metadata available for base
(1/2): openssl-1.0.2k-12.el7.x86_64.rpm                    | 492 kB   00:01     
(2/2): openssl-libs-1.0.2k-12.el7.x86_64.rpm               | 1.2 MB   00:03     
Total                                              545 kB/s | 1.7 MB  00:03     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Updating   : 1:openssl-libs-1.0.2k-12.el7.x86_64                          1/4 
  Updating   : 1:openssl-1.0.2k-12.el7.x86_64                               2/4 
  Cleanup    : 1:openssl-1.0.1e-51.el7_2.5.x86_64                           3/4 
  Cleanup    : 1:openssl-libs-1.0.1e-51.el7_2.5.x86_64                      4/4 
  Verifying  : 1:openssl-1.0.2k-12.el7.x86_64                               1/4 
  Verifying  : 1:openssl-libs-1.0.2k-12.el7.x86_64                          2/4 
  Verifying  : 1:openssl-libs-1.0.1e-51.el7_2.5.x86_64                      3/4 
  Verifying  : 1:openssl-1.0.1e-51.el7_2.5.x86_64                           4/4 

  openssl.x86_64 1:1.0.2k-12.el7                                                

Dependency Updated:
  openssl-libs.x86_64 1:1.0.2k-12.el7                                           

# openssl version
OpenSSL 1.0.2k-fips  26 Jan 2017

I then closed and reopened Firefox. I still saw the same issue for the Google and Wikipedia sites when I restored the prior session. But I noticed that I didn't see the security message in another tab that was open for I noticed that a couple of other HTTPS sites open in other Firefox tabs were also displaying normally, though when I tried, I saw the same issue. I refreshed the NoScript page and again it displayed normally. When I used Wireshark to capture the network traffic related to accessing that page, I noticed that after the client system sent a "Client Hello" packet to the server and the server subsequently sent a "Server Hello" packet to the client, that the server sent a packet that Wireshark categorized as "Certificate" in the Info column of its display. When I looked at the cipher selected by the server in the SSL section of the "Server Hello" packet, I saw that the Cipher Suite it selected from those listed in the "Client Hello" packet, which tells the server what cipher suites the client supports, it was Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f). You can find an explantation of the packets exchanged between client and server systems for TLS exchanges at Traffic Analysis of an SSL/TLS Session. That was the same cipher key I saw selected in the "Server Hello" packet from the Google web server.

Wireshark - Server Hello

I tried accessing several more sites via HTTPS. I couldn't access almost all of them, getting the same "Your connection is not secure" security message with "Error code: NS_ERROR_NET_INADEQUATE_SECURITY", but I was able to access the Juniper Networks website at

Since I was able to access the Google website using my MacBook Pro laptop on the same network as the Linux system, I thought maybe Firefox on the Linux system had an out-of-date public key certificate stored for the Google site. I put about:preferences#advanced in the address bar then clicked on the Certificates tab, then selected View Certificates (you can also get to that view by clicking on the icon with the 3 short, horizontal bars at the top, right-hand corner of the Firefox window and clicking on Advanced then seleting Certificates). When I clicked on the Servers tab, I saw a certificate for, but no certificates were listed for either any of the other sites producing the "your connection is not secure" message nor those where I didn't have a problem, such as the Juniper Networks site.

The Complete Wireshark Course: Go from Beginner to Advanced
The Complete Wireshark Course
Go from Beginner to Advanced
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Firefox Certificate Manager

And when I clicked on the View button to view the certificate details for the Google certificate, I saw that the serial number and the SHA1 and SHA-256 fingerprints were the same as when I checked the Google certificate on my MacBook Pro laptop running Firefox ESR 52.7.3 where I was not experiencing any problem accessing Google's website nor other sites.

I was finally able to resolve the problem after reading a comment at NS_ERROR_NET_INADEQUATE_SECURITY on opening where Richard W.M. Jones mentioned in a reply to the poster that an update to nss is needed. So I checked the version of the Network Security Services (NSS) rpm on the system and then upgraded it to the latest version with the yum upgrade nss command.

Udemy Generic Category (English)120x600
# rpm -qi nss
Name        : nss
Version     : 3.28.4
Release     : 15.el7_4
Architecture: x86_64
Install Date: Tue 21 Nov 2017 11:12:27 AM EST
Group       : System Environment/Libraries
Size        : 2501949
License     : MPLv2.0
Signature   : RSA/SHA256, Fri 20 Oct 2017 08:33:24 AM EDT, Key ID 24c6a8a7f4a80e
Source RPM  : nss-3.28.4-15.el7_4.src.rpm
Build Date  : Thu 19 Oct 2017 04:03:11 PM EDT
Build Host  :
Relocations : (not relocatable)
Packager    : CentOS BuildSystem <>
Vendor      : CentOS
URL         :
Summary     : Network Security Services
Description :
Network Security Services (NSS) is a set of libraries designed to
support cross-platform development of security-enabled client and
server applications. Applications built with NSS can support SSL v2
and v3, TLS, PKCS #5, PKCS #7, PKCS #11, PKCS #12, S/MIME, X.509
v3 certificates, and other security standards.
# yum upgrade nss
Loaded plugins: fastestmirror, langpacks
base                                                     | 3.6 kB     00:00     
epel/x86_64/metalink                                     |  19 kB     00:00     
extras                                                   | 3.4 kB     00:00     
updates                                                  | 3.4 kB     00:00     
vivaldi                                                  | 2.9 kB     00:00     
Loading mirror speeds from cached hostfile
 * base:
 * epel:
 * extras:
 * updates:
Resolving Dependencies
--> Running transaction check
---> Package nss.x86_64 0:3.28.4-15.el7_4 will be updated
--> Processing Dependency: nss = 3.28.4-15.el7_4 for package: nss-sysinit-3.28.4
--> Processing Dependency: nss(x86-64) = 3.28.4-15.el7_4 for package: nss-tools-
---> Package nss.x86_64 0:3.36.0-5.el7_5 will be an update
--> Processing Dependency: nss-util >= 3.36.0-1 for package: nss-3.36.0-5.el7_5.
--> Processing Dependency: nss-softokn(x86-64) >= 3.36.0-1 for package: nss-3.36
--> Processing Dependency: nspr >= 4.19.0 for package: nss-3.36.0-5.el7_5.x86_64
--> Processing Dependency: for package: nss-
--> Running transaction check
---> Package nspr.x86_64 0:4.13.1-1.0.el7_3 will be updated
---> Package nspr.x86_64 0:4.19.0-1.el7_5 will be an update
---> Package nss-softokn.x86_64 0:3.28.3-8.el7_4 will be updated
---> Package nss-softokn.x86_64 0:3.36.0-5.el7_5 will be an update
--> Processing Dependency: nss-softokn-freebl(x86-64) >= 3.36.0-5.el7_5 for pack
age: nss-softokn-3.36.0-5.el7_5.x86_64
---> Package nss-sysinit.x86_64 0:3.28.4-15.el7_4 will be updated
---> Package nss-sysinit.x86_64 0:3.36.0-5.el7_5 will be an update
---> Package nss-tools.x86_64 0:3.28.4-15.el7_4 will be updated
---> Package nss-tools.x86_64 0:3.36.0-5.el7_5 will be an update
---> Package nss-util.x86_64 0:3.28.4-3.el7 will be updated
---> Package nss-util.x86_64 0:3.36.0-1.el7_5 will be an update
--> Running transaction check
---> Package nss-softokn-freebl.i686 0:3.28.3-8.el7_4 will be updated
---> Package nss-softokn-freebl.x86_64 0:3.28.3-8.el7_4 will be updated
---> Package nss-softokn-freebl.i686 0:3.36.0-5.el7_5 will be an update
---> Package nss-softokn-freebl.x86_64 0:3.36.0-5.el7_5 will be an update
--> Finished Dependency Resolution

Dependencies Resolved

 Package                  Arch         Version              Repository     Size
 nss                      x86_64       3.36.0-5.el7_5       updates       835 k
Updating for dependencies:
 nspr                     x86_64       4.19.0-1.el7_5       updates       127 k
 nss-softokn              x86_64       3.36.0-5.el7_5       updates       315 k
 nss-softokn-freebl       i686         3.36.0-5.el7_5       updates       211 k
 nss-softokn-freebl       x86_64       3.36.0-5.el7_5       updates       222 k
 nss-sysinit              x86_64       3.36.0-5.el7_5       updates        62 k
 nss-tools                x86_64       3.36.0-5.el7_5       updates       514 k
 nss-util                 x86_64       3.36.0-1.el7_5       updates        78 k

Transaction Summary
Upgrade  1 Package (+7 Dependent packages)

Total download size: 2.3 M
Is this ok [y/d/N]: y
Downloading packages:
updates/7/x86_64/prestodelta                               | 255 kB   00:01     
Delta RPMs reduced 1.7 M of updates to 746 k (58% saved)
(1/8): nspr-4.13.1-1.0.el7_3_4.19.0-1.el7_5.x86_64.drpm    |  40 kB   00:00     
(2/8): nss-softokn-freebl-3.28.3-8.el7_4_3.36.0-5.el7_5.i6 |  91 kB   00:00     
(3/8): nss-softokn-3.28.3-8.el7_4_3.36.0-5.el7_5.x86_64.dr | 145 kB   00:00     
(4/8): nss-3.28.4-15.el7_4_3.36.0-5.el7_5.x86_64.drpm      | 330 kB   00:00     
(5/8): nss-sysinit-3.36.0-5.el7_5.x86_64.rpm               |  62 kB   00:00     
(6/8): nss-softokn-freebl-3.28.3-8.el7_4_3.36.0-5.el7_5.x8 |  94 kB   00:00     
(7/8): nss-util-3.28.4-3.el7_3.36.0-1.el7_5.x86_64.drpm    |  46 kB   00:00     
(8/8): nss-tools-3.36.0-5.el7_5.x86_64.rpm                 | 514 kB   00:00     
Finishing delta rebuilds of 4 package(s) (1.4 M)
Total                                              401 kB/s | 1.3 MB  00:03     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Updating   : nspr-4.19.0-1.el7_5.x86_64                                  1/16 
  Updating   : nss-util-3.36.0-1.el7_5.x86_64                              2/16 
  Updating   : nss-softokn-freebl-3.36.0-5.el7_5.x86_64                    3/16 
  Updating   : nss-softokn-3.36.0-5.el7_5.x86_64                           4/16 
  Updating   : nss-sysinit-3.36.0-5.el7_5.x86_64                           5/16 
  Updating   : nss-3.36.0-5.el7_5.x86_64                                   6/16 
  Updating   : nss-tools-3.36.0-5.el7_5.x86_64                             7/16 
  Updating   : nss-softokn-freebl-3.36.0-5.el7_5.i686                      8/16 
  Cleanup    : nss-softokn-freebl-3.28.3-8.el7_4                           9/16 
  Cleanup    : nss-tools-3.28.4-15.el7_4.x86_64                           10/16 
  Cleanup    : nss-3.28.4-15.el7_4.x86_64                                 11/16 
  Cleanup    : nss-sysinit-3.28.4-15.el7_4.x86_64                         12/16 
  Cleanup    : nss-softokn-3.28.3-8.el7_4.x86_64                          13/16 
  Cleanup    : nss-util-3.28.4-3.el7.x86_64                               14/16 
  Cleanup    : nss-softokn-freebl-3.28.3-8.el7_4                          15/16 
  Cleanup    : nspr-4.13.1-1.0.el7_3.x86_64                               16/16 
  Verifying  : nss-util-3.36.0-1.el7_5.x86_64                              1/16 
  Verifying  : nspr-4.19.0-1.el7_5.x86_64                                  2/16 
  Verifying  : nss-sysinit-3.36.0-5.el7_5.x86_64                           3/16 
  Verifying  : nss-softokn-freebl-3.36.0-5.el7_5.i686                      4/16 
  Verifying  : nss-tools-3.36.0-5.el7_5.x86_64                             5/16 
  Verifying  : nss-3.36.0-5.el7_5.x86_64                                   6/16 
  Verifying  : nss-softokn-freebl-3.36.0-5.el7_5.x86_64                    7/16 
  Verifying  : nss-softokn-3.36.0-5.el7_5.x86_64                           8/16 
  Verifying  : nspr-4.13.1-1.0.el7_3.x86_64                                9/16 
  Verifying  : nss-sysinit-3.28.4-15.el7_4.x86_64                         10/16 
  Verifying  : nss-util-3.28.4-3.el7.x86_64                               11/16 
  Verifying  : nss-softokn-3.28.3-8.el7_4.x86_64                          12/16 
  Verifying  : nss-softokn-freebl-3.28.3-8.el7_4.i686                     13/16 
  Verifying  : nss-3.28.4-15.el7_4.x86_64                                 14/16 
  Verifying  : nss-tools-3.28.4-15.el7_4.x86_64                           15/16 
  Verifying  : nss-softokn-freebl-3.28.3-8.el7_4.x86_64                   16/16 

  nss.x86_64 0:3.36.0-5.el7_5                                                   

Dependency Updated:
  nspr.x86_64 0:4.19.0-1.el7_5                                                  
  nss-softokn.x86_64 0:3.36.0-5.el7_5                                           
  nss-softokn-freebl.i686 0:3.36.0-5.el7_5                                      
  nss-softokn-freebl.x86_64 0:3.36.0-5.el7_5                                    
  nss-sysinit.x86_64 0:3.36.0-5.el7_5                                           
  nss-tools.x86_64 0:3.36.0-5.el7_5                                             
  nss-util.x86_64 0:3.36.0-1.el7_5                                              


After I upgraded NSS and then closed and reopened Firefox, the problem was solved. I was able to use the Google and Bing search engines and visit the other sites that hadn't been accessible via HTTPS previously.

Related articles:

  1. Installing Wireshark under CentOS
  2. Capturing and filtering data with Wireshark


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