Government of the Republic of Trinidad and Tobago

TTCSIRT-118.051418: TT-CSIRT Advisory – Mozilla Security Updates

TTCSIRT-118.051418: TT-CSIRT Advisory – Mozilla Security Updates

Mozilla has released a security update stating that the following vulnerabilities have been discovered in Mozilla Firefox and Firefox Extended Support Release (ESR):

a) A buffer overflow was found during UTF8 to Unicode string conversion within JavaScript with extremely large amounts of data. This vulnerability requires the use of a malicious or vulnerable legacy extension in order to occur – (CVE-2018-5178).

b) A mechanism to bypass Content Security Policy (CSP) protections on sites that have a script-src policy of ‘strict-dynamic’. If a target website contains an HTML injection flaw an attacker could inject a reference to a copy of the require.js library that is part of Firefox’s Developer Tools, and then use a known technique using that library to bypass the CSP restrictions on executing injected scripts – (CVE-2018-5175).

c) An integer overflow can occur in the Skia library due to 32-bit integer use in an array without integer overflow checks, resulting in possible out-of-bounds writes. This could lead to a potentially exploitable crash triggerable by web content – (CVE-2018-5159).

d) A use-after-free vulnerability can occur during WebGL operations. While this results in a potentially exploitable crash, the vulnerability is limited because the memory is freed and reused in a brief window of time during the freeing of the same callstack – (CVE-2018-5180).

e) A use-after-free vulnerability can occur while adjusting layout during SVG animations with text paths. This results in a potentially exploitable crash – (CVE-2018-5155).

f) A use-after-free vulnerability can occur while enumerating attributes during SVG animations with clip paths. This results in a potentially exploitable crash – (CVE-2018-5154).

g) A vulnerability exists in XSLT during number formatting where a negative buffer size may be allocated in some instances, leading to a buffer overflow and crash if it occurs – (CVE-2018-5177).

h) Content Security Policy (CSP) is not applied correctly to all parts of multipart content sent with the multipart/x-mixed-replace MIME type. This could allow for script to run where CSP should block it, allowing for cross-site scripting (XSS) and other attacks – (CVE-2018-5164).

i) Backported select changes in the Skia library to the ESR52 branch of Firefox. These changes correct memory corruption issues including invalid buffer reads and writes during graphic operations – (CVE-2018-5183).

Successful exploitation of the most severe of these vulnerabilities could allow for arbitrary code execution. Depending on the privileges associated with the user, an attacker could then install programs view, change or delete data or even create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

Further information on these vulnerabilities and how they can be mitigated can be found on the Mozilla Website at