CVE-2017-7805 : What You Need to Know

In September 2017, CVE-2017-7805 was published, affecting Mozilla's Firefox, Firefox ESR, and Thunderbird. The vulnerability involves TLS 1.2 handshake hashes, potentially leading to a use-after-free scenario and exploitable crashes.

Understanding CVE-2017-7805

This CVE identifies a critical vulnerability in TLS 1.2 handshake hash generation in Mozilla products.

What is CVE-2017-7805?

During TLS 1.2 exchanges, handshake hashes are created, pointing to a message buffer. If the handshake transcript exceeds the buffer's capacity, a new buffer is allocated, leaving a pointer to the old buffer. This can result in a use-after-free scenario when computing handshake hashes, leading to exploitable crashes.

The Impact of CVE-2017-7805

The vulnerability affects Firefox versions less than 56, Firefox ESR versions less than 52.4, and Thunderbird versions less than 52.4. Exploitation could result in crashes and potentially harmful consequences.

Technical Details of CVE-2017-7805

This section delves into the technical aspects of the vulnerability.

Vulnerability Description

The flaw arises from the mishandling of handshake hashes in TLS 1.2 exchanges, potentially causing a use-after-free scenario.

Affected Systems and Versions

Firefox < 56
Firefox ESR < 52.4
Thunderbird < 52.4

Exploitation Mechanism

When handshake hashes exceed buffer capacity, a new buffer is allocated, leading to a use-after-free scenario during subsequent hash calculations.

Mitigation and Prevention

Protecting systems from CVE-2017-7805 is crucial to maintaining security.

Immediate Steps to Take

Update affected Mozilla products to versions that address the vulnerability.
Monitor security advisories for patches and updates.

Long-Term Security Practices

Regularly update software to the latest versions.
Implement secure coding practices to prevent similar vulnerabilities.

Patching and Updates

Apply patches provided by Mozilla promptly to mitigate the risk of exploitation.