Mozilla has issued a new Firefox browser update with fixes for four critical vulnerabilities and a number of less severe issues.
In Firefox 39, a total of four critical vulnerabilities, two high-level flaws and six moderate bugs have been patched among a total of 13 fixes. According to the Mozilla security advisory, security issues relate to use-after-free vulnerabilities, poor validation processes, buffer overflow problems and a variety of memory problems.
Two of the most critical issues are use-after-free vulnerabilities. When using XMLHttpRequest in concert with either shared or dedicated workers, errors occur when the XMLHttpRequest object is attached to a worker -- but that object is incorrectly deleted while still in use. This, in turn, can lead to exploitable crashes.
In addition, seven vulnerabilities, lumped together under one critical bug advisory, relate to released browser code. Three vulnerabilities were discovered as uses of uninitialized memory, one related to poor validation leading to an exploitable crash, one read of unowned memory in .zip files, and two issues led to buffer overflows.
Separately, these bugs could not be exploited easily through web content, but according to Mozilla "are vulnerable if a mechanism can be found to trigger them."
Another critical vulnerability is a use-after-free flaw which occurs when a Content Policy modifies the Document Object Model to remove a DOM object. An error in microtask implementation can lead to an exploitable browser crash -- however, this flaw cannot generally be exploited through Thunderbird email because scripting is disabled.
The last critical vulnerability relates to memory safety bugs in the browser engine. Mozilla says a number of bugs could corrupt memory "under certain circumstances," and may be exploited to run arbitrary code.
Other bugs fixed include signature validation errors, privilege escalation flaws, ServerKeyExchange skipping bugs and type confusion problems.
Read on: Top picks
- Security researcher casually drops Adobe Reader, Windows critical vulnerability bomb
- Father's Day 2015: A tech gift pack for under $100
- Severe iOS bug prompts iCloud password theft
- Malwarebytes snaps up Junkware Removal Tool
- LOT airline hack signals the first in emerging cyberthreat trend
- Hackers control medical pumps to administer fatal doses