As technology advances, so too do the threats we face when it comes to cybersecurity. One such example is the CVE-2014-1491 vulnerability found in Mozilla Network Security Services (NSS) before version 3.15.4. This vulnerability affects Mozilla Firefox, Firefox ESR, Thunderbird, and SeaMonkey, among other products.

In this long-read post, we will take an in-depth look at this vulnerability, examining its code snippits and highlighting the exploit details. Additionally, we will provide links to the original references and explanations in simple American language to ensure even novice users grasp the concept of the CVE-2014-1491 flaw.


Before diving into the intricacies of CVE-2014-1491, it’s important to look at the broader technology involved: Mozilla Network Security Services (NSS). NSS is a set of libraries designed to implement network security protocols and provide support for Secure Sockets Layer (SSL), Transport Layer Security (TLS), and several other cryptographic functionalities.

The CVE-2014-1491 vulnerability revolves around the improper restriction of public values in Diffie-Hellman key exchanges within NSS implementations. As a result, attackers can more easily bypass cryptographic protection mechanisms in ticket handling by leveraging use of a particular value.

Exploit Details

Now that we’ve set the stage with a brief background on NSS and the core issue at play, let’s delve into the exploit details.

The vulnerability in the Diffie-Hellman key exchange process allows attackers to potentially intercept and decrypt SSL/TLS connections. This is accomplished by sending the "small subgroup" value, which will ultimately result in communication utilizing an easily cracked session key.

Here's a code snippet showcasing the public key value check in question

static SECStatus
dh_validate_public_key(const unsigned char *pubKeyData, 
                       const unsigned char *prime, unsigned int keySize)
    /* Check for invalid public key values */
    if ((memcmp(pubKeyData, prime, keySize) >= ) ||
        (memcmp(pubKeyData,, dh_one.len) <= )) {
        return SECFailure;

As seen in the snippet, the public key value is checked against the prime and the value 1. Unfortunately, this check fails to account for the "small subgroup" value, which is the root cause of the CVE-2014-1491 vulnerability.

For more information on the code and the patch, find the original Mozilla security advisory here

Original Advisory: Mozilla Foundation Security Advisory 2014-13

Mitigation Measures

To defend against this vulnerability and potential exploits, the first step is updating your software to the latest version. It is crucial to use the following versions:

SeaMonkey 2.24 or later

In addition to updating your software, it is also advisable to ensure that secure connections are not utilizing potentially vulnerable cryptographic algorithms.


Understanding the CVE-2014-1491 vulnerability provides insight into the importance of implementing secure algorithms and robust code checks when deploying network security protocols. By remaining vigilant and keeping your software updated, you can minimize the risk of cybersecurity breaches and ensure your sensitive data remains secure.


Published on: 02/06/2014 05:44:00 UTC
Last modified on: 07/31/2020 20:33:00 UTC