Meltdown and Spectre exploit critical vulnerabilities in modern processors. These hardware bugs allow programs to steal data which is currently processed on the computer. While programs are typically not permitted to read data from other programs, a malicious program can exploit Meltdown and Spectre to get hold of secrets stored in the memory of other running programs. This might include your passwords stored in a password manager or browser, your personal photos, emails, instant messages and even business-critical documents.
Meltdown and Spectre work on personal computers, mobile devices, and in the cloud. Depending on the cloud provider's infrastructure, it might be possible to steal data from other customers.Meltdown and Spectre work on personal computers, mobile devices, and in the cloud. Depending on the cloud provider's infrastructure, it might be possible to steal data from other customers.
The security of computer systems fundamentally relies on memory isolation, e.g., kernel address ranges are marked as non-accessible and are protected from user access. In this paper, we present Meltdown. Meltdown exploits side effects of out-of-order execution on modern processors to read arbitrary kernel-memory locations including personal data and passwords. Out-of-order execution is an indispensable performance feature and present in a wide range of modern processors. The attack is independent of the operating system, and it does not rely on any software vulnerabilities. Meltdown breaks all security assumptions given by address space isolation as well as para-virtualized environments and, thus, every security mechanism building upon this foundation. On affected systems, Meltdown enables an adversary to read the memory of other processes or virtual machines in the cloud without any permissions or privileges, affecting millions of customers and virtually every user of a personal computer. We show that the KAISER defense mechanism for KASLR  has the important (but inadvertent) side effect of impeding Meltdown. We stress that KAISER must be deployed immediately to prevent large-scale exploitation of this severe information leakage.
Modern processors use branch prediction and speculative execution to maximize performance. For example, if the destination of a branch depends on a memory value that is in the process of being read, CPUs will try to guess the destination and attempt to execute ahead. When the memory value finally arrives, the CPU either discards or commits the speculative computation. Speculative logic is unfaithful in how it executes, can access to the victim’s memory and registers, and can perform operations with measurable side effects.
Spectre attacks involve inducing a victim to speculatively perform operations that would not occur during correct program execution and which leak the victim’s confidential information via a side channel to the adversary. This paper describes practical attacks that combine methodology from side channel attacks, fault attacks, and return-oriented programming that can read arbitrary memory from the victim’s process. More broadly, the paper shows that speculative execution implementations violate the security assumptions underpinning numerous software security mechanisms, including operating system process separation, static analysis, containerization, just-in-time (JIT) compilation, and countermeasures to cache timing/side-channel attacks. These attacks represent a serious threat to actual systems since vulnerable speculative execution capabilities are found in microprocessors from Intel, AMD, and ARM that are used in billions of devices.
Protect Against Meltdown and Spectre CPU Flaws
Some, including US-CERT, have suggested the only true patch for these issues is for chips to be replaced, but this solution seems to be impractical for the general user and most companies. Vendors have made significant progress in rolling out fixes and firmware updates. While the Meltdown flaw has already been patched by most companies like Microsoft, Apple and Google, Spectre is not easy to patch and will haunt people for quite some time.
Here's the list of available patches from major tech manufacturers:
Windows OS (7/8/10) and Microsoft Edge/IE
Microsoft has already released an out-of-band security update (KB4056892) for Windows 10 to address the Meltdown issue and will be releasing patches for Windows 7 and Windows 8 on January 9th.
But if you are running a third-party antivirus software then it is possible your system won’t install patches automatically. So, if you are having trouble installing the automatic security update, turn off your antivirus and use Windows Defender or Microsoft Security Essentials.
"The compatibility issue is caused when antivirus applications make unsupported calls into Windows kernel memory," Microsoft noted in a blog post. "These calls may cause stop errors (also known as blue screen errors) that make the device unable to boot."
Google Chrome Web Browser
Google has scheduled the patches for Meltdown and Spectre exploits on January 23 with the release of Chrome 64, which will include mitigations to protect your desktop and smartphone from web-based attacks.
In the meantime, users can enable an experimental feature called "Site Isolation" that can offer some protection against the web-based exploits but might also cause performance problems.
"Site Isolation makes it harder for untrusted websites to access or steal information from your accounts on other websites. Websites typically cannot access each other's data inside the browser, thanks to code that enforces the Same Origin Policy." Google says.
Here's how to turn on Site Isolation:
- Copy chrome://flags/#enable-site-per-process and paste it into the URL field at the top of your Chrome web browser, and then hit the Enter key.
- Look for Strict Site Isolation, then click the box labeled Enable.
- Once done, hit Relaunch Now to relaunch your Chrome browser.
Firefox Web Browser
Mozilla has released Firefox version 57.0.4 which includes mitigations for both Meltdown and Spectre timing attacks. So users are advised to update their installations as soon as possible.
"Since this new class of attacks involves measuring precise time intervals, as a partial, short-term mitigation we are disabling or reducing the precision of several time sources in Firefox," Mozilla software engineer Luke Wagner wrote in a blog post.
VMware and Citrix
A global leader in cloud computing and virtualization, VMware, has also released a list of its products affected by the two attacks and security updates for its ESXi, Workstation, and Fusion products to patch against Meltdown attacks.
On the other hand, another popular cloud computing and virtualization vendor Citrix did not release any security patches to address the issue. Instead, the company guided its customers and recommended them to check for any update on relevant third-party software.