Vendors shipping products based on Chromium might wish to rate the severity of security issues in the products they release. This document contains guidelines for how to rate these issues. Check out our security release management page for guidance on how to release fixes based on severity.
Any significant mitigating factors, such as unusual or additional user interaction, or running Chrome with a specific command line flag or non-default feature enabled, may reduce an issue’s severity by one or more levels. Also note that most crashes do not indicate vulnerabilities. Chromium is designed to crash in a controlled manner (e.g., with a
__debugBreak) when memory is exhausted or in other exceptional circumstances.
Critical severity issues allow an attacker run arbitrary code on the underlying platform with the user's privileges.
They are normally assigned priority Pri-0 and assigned to the current stable milestone (or earliest milestone affected). For critical severity bugs, SheriffBot will automatically assign the milestone.
Critical vulnerability details may be made public in 60 days, in accordance with Google's general vulnerability disclosure recommendations, or faster (7 days) if there is evidence of active exploitation.
Note that the individual bugs that make up the chain will have lower severity ratings.
High severity vulnerabilities allow an attacker to execute code in the context of, or otherwise impersonate other origins. Bugs which would normally be critical severity with unusual mitigating factors may be rated as high severity. For example, renderer sandbox escapes fall into this category as their impact is that of a critical severity bug, but they require the precondition of a compromised renderer.
They are normally assigned priority Pri-1 and assigned to the current stable milestone (or earliest milestone affected). For high severity bugs, SheriffBot will automatically assign the milestone.
For high severity vulnerabilities, we aim to deploy the patch to all Chrome users in under 60 days.
Medium severity bugs allow attackers to read or modify limited amounts of information, or are not harmful on their own but potentially harmful when combined with other bugs. This includes information leaks that could be useful in potential memory corruption exploits, or exposure of sensitive user information that an attacker can exfiltrate. Bugs that would normally rated at a higher severity level with unusual mitigating factors may be rated as medium severity.
They are normally assigned priority Pri-1 and assigned to the current stable milestone (or earliest milestone affected). If the fix seems too complicated to merge to the current stable milestone, they may be assigned to the next stable milestone.
Low severity vulnerabilities are usually bugs that would normally be a higher severity, but which have extreme mitigating factors or highly limited scope.
They are normally assigned priority Pri-2. Milestones can be assigned to low severity bugs on a case-by-case basis, but they are not normally merged to stable or beta branches.