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Version 2024.3 Changelog

In the 2024.3 release of the Stakeholder-Specific Vulnerability Classification (SSVC) system, we've made a number of significant changes:

New Web Site

This release debuts the web site to serve as the front-door for all things SSVC.

  • Diátaxis Framework - We adopted the Diátaxis Framework as a document organization framework for SSVC documentation. High level content categories are: tutorials, how-to, topics, and reference. What used to be a linear paper format is now sectioned off into more digestible pieces.
  • More call-outs and examples - With our adoption of Material for MkDocs as the underlying toolkit to construct our web site, we were able to better highlight examples, tips, and sidebar topics through the use of call-out boxes throughout the site.

New and Revised Content

  • Expanded Content - We've included more examples of Decision Points and the like directly inline where they're mentioned so readers don't need to keep flipping back and forth to their definitions for reference.
  • Bootstrapping advice - Added a Getting Started with SSVC process to help organizations go from being potential SSVC users to being actual SSVC users. This process is based on both our own experience helping organizations adopt SSVC as well as a few field reports of SSVC adoption from the community.
  • Putting the Pieces Together - Added a Putting the Pieces Together page explaining some of our philosophy regarding how to use SSVC to model decisions. SSVC provides you with the pieces and some instructions on how to assemble them, but you can customize it however you like.
  • Acuity Ramp - Added an Acuity Ramp explainer to show how an organization can grow into a decision model over time.
  • Community Engagement - Included in the new web site are a number of suggested ways for the community to interact with and contribute to the SSVC.

Versioned Objects

  • Semantic Versioning for Decision Points and Decision Point Groups - Introduced Semantic Versioning (SemVer) for Decision Points and Decision Point Groups to improve communication around decision points and decision models
  • Calendar Versioning for SSVC as a whole - With the introduction of SemVer for Decision Points and Decision Point Groups, it started to make less sense for us to talk in terms of "SSVC v2.2", especially as we were simultaneously moving away from a PDF document-focused development model towards a more flexible web-based documentation model. Beginning with this version, we anticipate that future tagged releases will use Calendar Versioning (CalVer) instead of SemVer.

Experimental & Emerging Features

There are a few improvements we've begun but have not yet fully finished, and that are largely undocumented. Most of these in the current release are python-centric. Here's a brief overview for those who want to poke around at code.

  • SSVC Python module - This release introduces the ssvc python module to allow us to more easily work with Decision Points, Decision Point Groups, Outcomes, and Policies that map from Decision Points to Outcomes. We expect to have more to say about this module in the future, but for now it's geared towards helping us produce the site documentation.
  • Policy Generator - We're prototyping a Python tool that can generate a starting policy given any combination of a Decision Point Group and Outcomes. It's not ready for prime-time yet, but folks with a bit of python skill might be in a position to try it out.
  • More Decision Points and Outcomes - In the process of exercising our Semantic Versioning rules for decision points and groups, we needed some examples of versioning events for discussion purposes. As a result, the ssvc.decision_points.cvss and ssvc.dp_groups.cvss modules contain python implementations of CVSS vector elements from CVSS v1, v2, v3, v3.1, and v4. We anticipate some of these coming in handy in the future as we look toward modeling other decisions potentially based on CVSS vector elements as well as other decision points from SSVC and elsewhere. We also included decision points and groups from CISA's customized SSVC implementation.

Other project infrastructure improvements

  • Shifted from PDF-oriented to web-oriented workflow
  • Adopted MkDocs and Material for MkDocs for static site production
  • Adopted Markdown Any Decision Records to preserve rationale and record decisions that are of significant impact to the project
  • Added documentation to the SSVC project wiki with tips for current and future contributors.
  • Began using Github's Dependabot to help maintain dependency versions.

Version 2.1 (2023.7) Changelog

This section summarizes the changes between SSVC 2.1 and SSVC version 2.0. The details of what changes were made can be viewed on the SSVC Github under the SSVC v2.1 milestone.

  • Introduced a demo SSVC Calc App which became the basis for CISA's SSVC Calculator
  • Updated Deployer tree to use Automatable instead of Utility, which reduced the size from 108 leaf nodes to 72.
  • Adjusted Deployer tree decisions based on stakeholder feedback
  • Adjusted Supplier tree decisions based on stakeholder feedback
  • Added section on Sharing Trees With Others including a discussion of decision point scope and decision tree scope.
  • Improved clarity of time-sensitivity of some decision points in Representing Information for Decisions About Vulnerabilities
  • Improved description of Mission Impact
  • Improved consistency of Public Safety Impact usage throughout the document and tooling
  • Improved consistency of Human Impact usage throughout the document
  • Clarified that known default passwords are an example of Exploitation:PoC
  • Clarified that unreachable code (as in unused library features) are System Exposure:small
  • Mention DoD MEF definition in Mission Impact
  • Updated references to EPSS to reflect recent publications
  • Refactored markdown files to better track chapter and section numbering, improving findability when editing
  • Automated HTML and PDF generation into a Github Workflow
  • Updated python tools to maintain sync with current SSVC decision models
  • Consolidated the SSVC document style guide into a single file in the repository
  • Miscellaneous typo fixes and readability improvements (e.g., headings, bulleted lists)

Version 2 (2021.5) Changelog

This section summarizes the changes between SSVC version 2 and SSVC version 1.1 as published at the Workshop on the Ecnomics of Information Security (WEIS 2020). The details of what changes were made can be viewed on the SSVC GitHub issues closed under the SSVC v2 Development project. We addressed about 60 issues. About 10 issues identified “bugs” or errors in version 1.1. About 20 issues improved documentation of tools or improved the clarity of document text. The remaining 30 issues were focused on enhancing SSVC based on feedback received on version 1, though several of the bug fixes and documentation improvements also provided improvements. This section focuses on changes that provided enhancements.

Coordinator stakeholder

Version 1 only considered two stakeholders: those who make software, and those who use information systems. Version 2 introduces a coordinator stakeholder and two distinct decisions for that stakeholder group: vulnerability intake triage and publication about a vulnerability. These decisions use some existing decision points, but also introduce six new decision points to support coordinators in making these decisions. The coordinator stakeholder is based on CERT/CC's experience coordinating vulnerabilities.

Terminology changes

Some terms have been adjusted to better align with other usage in the field or based on feedback. Therefore, “patch developer” became supplier and “patch applier” became deployer. These terms in version 2 better reflect the stakeholder's relationship to the vulnerable component and also help keep clear that SSVC is about prioritization of work items in vulnerability management, not just patches. We have also generally removed the word patch and instead use the more general “remediation” for a complete fix and “mitigation” for actions that reduce risk but do not remove a vulnerability from a system. “Virulence” was renamed Automatable in a effort to be more direct and clear, rather than relying on an epidemiology metaphor. We changed “out-of-band” to out-of-cycle.

Some concepts needed to be clarified or added. These changes are a bit more substantive than the above terminology changes, but are similar. For example, we clarified how end-of-life products are prioritized with SSVC. We also clarified in Scope concepts around vulnerability identificatin and disambiguation. Version 2 adopts an explicit definition of risk (from ISO Guide 73). We also differentiated between vulnerability risk, or that risk arising from an unmanaged vulnerability in an information system, and change risk, or that risk from modifying or updating an information system to mitigate or remediate a vulnerability. SSVC version 2 focuses on assessing and managing vulnerability risk, not change risk. This stance was not explicit in SSVC version 1.

Improvements to decision points

Version 1 had a decision point for well-being impact that was shared between supplier and deployer stakeholders. Since these types of stakeholder have access to different information about safety and well-being, Version 2 splits this concept into Public Safety Impact and Situated Safety Impact. The underlying definition remains largely the same. However, Public Safety Impact has fewer output options (it is less granular) in recognition that a supplier or coordinator has less information about the context of deployment than a deployer does.

In addition, based on feedback from SSVC users, the SSVC version 2 recommended applier tree makes use of a combined value for Mission Impact and Situated Safety Impact. The intuition behind this change is that if a person is going to die OR the organization is going to fail (for example, go bankrupt), then the organization will likely want to act with highest priority. Either situation is sufficient to increase the priority, and there do not appear to be situations where a low Mission Impact would mitigate a high Situated Safety Impact or vice versa. On the other hand, a low Utility or System Exposure may mitigate a high mission or well-being impact. So the Version 2 recommended tree is more usable than the Version 1 tree, thanks to these changes.

Tree management and communication tools

The section Tree Construction and Customization Guidance is largely new or revised. We produced new software tools for interacting with SSVC, which are documented in that section. Version 2 adds reasoning behind why a stakeholder might customize a decision tree, what aspects of the tree are best to customize, tools for encoding custom trees in JSON, and scripts for visualizing custom trees.

Similarly, the section on Guidance on Communicating Results is largely new. The section presents both an abbreviated and unabridged format for communicating SSVC information about a vulnerability. This communication may be connected to the formats for communicating a whole decision tree. Version 2 also addresses several other questions about SSVC information management, such as handling information changes over time, partial information, sourcing information for each decision point, and how collection and analysis of SSVC decision points can be automated.

Version 1.0 (2019.12) Changelog

Initial release