Pierluigi Paganini July 11, 2018

A team of researchers has discovered new variant of the famous Spectre attack (Spectre 1.1), and Intel has paid a $100,000 bug bounty as part of its bug bounty program.

Intel has paid out a $100,000 bug bounty for new vulnerabilities that are related to the first variant of the Spectre attack (CVE-2017-5753), for this reason, they have been tracked as Spectre 1.1 (CVE-2018-3693) and Spectre 1.2.

Intel credited Kiriansky and Waldspurger for the vulnerabilities to Intel and paid out $100,000 to Kiriansky via the bug bounty program on HackerOne.

Early 2018, researchers from Google Project Zero disclosed details of both Spectre Variants 1 and 2 (CVE-2017-5753 and CVE-2017-5715) and Meltdown (CVE-2017-5754).

Both attacks leverage the “speculative execution” technique used by most modern CPUs to optimize performance.

The team of experts composed of Vladimir Kiriansky of MIT and Carl Waldspurger of Carl Waldspurger Consulting discovered two new variants of Spectre Variant 1.

Back to the present, the Spectre 1.1 issue is a bounds-check bypass store flaw that could be exploited by attackers to trigger speculative buffer overflows and execute arbitrary code on the vulnerable processor.

This code could potentially be exploited to exfiltrate sensitive data from the CPU memory, including passwords and cryptographic keys.

“We introduce Spectre1.1, a new Spectre-v1 variant that leverages speculative stores to create speculative buffer overflows. Much like classic buffer overflows, speculative out-ofbounds stores can modify data and code pointers. Data-value attacks can bypass some Spectre-v1 mitigations, either directly or by redirecting control flow.” reads the research paper.

“Control-flow attacks enable arbitrary speculative code execution, which can bypass
fence instructions and all other software mitigations for previous speculative-execution attacks.”

The second sub-variant discovered by the experts, called Spectre1.2 is a  read-only protection bypass

It depends on lazy PTE enforcement that is the same mechanism exploited for the original Meltdown attack.

“Spectre3.0, aka Meltdown [39], relies on lazy enforcement of User/Supervisor protection flags for page-table entries (PTEs). The same mechanism can also be used to bypass the Read/Write PTE flags. We introduce Spectre1.2, a minor variant of Spectre-v1 which depends on lazy PTE enforcement, similar to Spectre-v3.”In a Spectre1.2 attack, speculative stores are allowed to overwrite read-only data, code pointers, and code metadata, including vtables, GOT/IAT, and control-flow mitigation metadata. As a result, sandboxing that depends on hardware enforcement of read-only memory is rendered ineffective.,” continues the research paper.

ARM confirmed that Spectre 1.1 flaw affects also its processor but avoided to mention flawed ARM CPUs.

Mayor tech firms, including Microsoft, Red Hat and Oracle have released security advisories, confirming that they are investigating the issues and potential effects of the new Spectre variants.

“Microsoft is aware of a new publicly disclosed class of vulnerabilities referred to as “speculative execution side-channel attacks” that affect many modern processors and operating systems including Intel, AMD, and ARM. Note: this issue will affect other systems such as Android, Chrome, iOS, MacOS, so we advise customers to seek out guidance from those vendors.” reads the advisory published by Microsoft.

“An attacker who successfully exploited these vulnerabilities may be able to read privileged data across trust boundaries. In shared resource environments (such as exists in some cloud services configurations), these vulnerabilities could allow one virtual machine to improperly access information from another.” 

Pierluigi Paganini

(Security Affairs – Spectre 1.1, hacking)

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