---
title: "Vulnerability Knowledge Base | BCBS\n    | Ubuntu"
description: Bounds Check Bypass Store (BCBS) – Spectre 1.1, Spectre 1.2 (CVE-2018-3693)
url: https://ubuntu.com/security/vulnerabilities/bcbs?format=md
keywords: index, follow
---

1. [Vulnerability knowledge base](https://ubuntu.com/security/vulnerabilities)
2. [View all](https://ubuntu.com/security/vulnerabilities/view-all)
3. BCBS

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# BCBS

Bounds Check Bypass Store (BCBS) – Spectre 1.1, Spectre 1.2 (CVE-2018-3693)

Published

10 July 2018

Updated

1 year, 6 months ago

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Vladimir Kiriansky and Carl Waldspurger discovered that systems with microprocessors utilizing speculative execution and branch prediction may allow unauthorized disclosure of information to an attacker with local user access via a speculative buffer overflow and side channel analysis. This issue is similar to [CVE-2017-5753](https://ubuntu.com/security/CVE-2017-5753) with the difference being that [CVE-2017-5753](https://ubuntu.com/security/CVE-2017-5753) was specific to bypassing the bounds check on a load and this issue pertains to bypassing the bounds check on a store. Intel recommends similar mitigation techniques - utilize `lfence` as a barrier between bounds check and store to ensure that the bounds check operation completes before the store is executed. Analysis is ongoing to see whether additional code locations require `lfence` placements. Users should update their systems regularly to ensure that they have the latest security fixes in place. The `lfence` instruction was added via microcode. Users should ensure that they are utilizing the latest microcode to ensure that side channel remediations are in place.

For more information on these issues, please see the following reference documents:

* [Intel Analysis of Speculative Execution Side Channels](https://software.intel.com/sites/default/files/managed/b9/f9/336983-Intel-Analysis-of-Speculative-Execution-Side-Channels-White-Paper.pdf) Revision 4.0, Updated July 2018
* [Intel Analyzing potential bounds check bypass vulnerabilities](https://software.intel.com/sites/default/files/managed/4e/a1/337879-analyzing-potential-bounds-Check-bypass-vulnerabilities.pdf)
* [Intel Speculative Execution Branch Prediction Side Channel and Branch Prediction Analysis Method](https://01.org/security/advisories/intel-oss-10002)
* [Speculative Buffer Overflows: Attacks and Defenses](https://people.csail.mit.edu/vlk/spectre11.pdf)
* [Speculative Load Hardening](https://docs.google.com/document/d/1wwcfv3UV9ZnZVcGiGuoITT_61e_Ko3TmoCS3uXLcJR0/edit#heading=h.yz0cr3jlliwx)

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## Timeline

* 2018 July 10 at 17:00 UTC: the issue is made public