A software program invoice of supplies (SBOM) gives transparency into the weather of an built-in software program product. Such transparency is essential to figuring out system vulnerabilities and thus mitigating potential safety dangers. There may be rising curiosity in utilizing SBOMs to help software program provide chain threat administration. In September 2024 Military leaders signed a memorandum requiring SBOMs for vendor-supplied software program. Extra just lately, the Division of Protection (DoD) Chief Info Officer, by way of its Software program Quick Observe Program, is requiring that software program distributors submit their SBOMs, in addition to these from third-party assessors, to allow detection of variances between SBOMs for a similar software program.
Completely different SBOM instruments ought to produce related data for a chunk of software program at a given level in its lifecycle, however this isn’t at all times the case. The divergence of SBOMs for particular person items of software program can undermine confidence in these vital paperwork for software program high quality and safety. This weblog put up outlines our workforce’s latest findings on why SBOMs diverge and recommends seven methods to enhance SBOM accuracy.
SBOM Harmonization Plugfest
The SEI’s 2024 SBOM Harmonization Plugfest mission, sponsored by the Cybersecurity and Infrastructure Safety Company (CISA), aimed to uncover the basis causes of SBOM divergence, equivalent to imprecise definitions or requirements, how uncertainty is addressed, or different implementation choices. The SEI introduced collectively SBOM instrument distributors, requirements producers, and others within the SBOM neighborhood to provide pattern SBOMs for evaluation. The just lately launched Software program Invoice of Supplies (SBOM) Harmonization Plugfest 2024, on which this put up is predicated, outlines our workforce’s findings, evaluation, and proposals to assist SBOM producers generate extra constant and dependable SBOMs.
We requested Plugfest contributors to generate and submit SBOMs based mostly on 9 software program targets chosen as a consultant pattern of varied programming languages as seen in Desk 1 beneath.
The SEI gained approval from most contributors to make their submissions public. These SBOMs that have been accepted for launch are now obtainable at SEI’s GitHub website.
Overview and Evaluation of Submitted SBOMs
We obtained 243 SBOMs from 21 Plugfest contributors. To make sure anonymity and to forestall any bias in our assessment, we anonymized participant names by assigning alphanumeric codes to every. One participant, who was assigned the code Y2, submitted many extra SBOMs (102) than all of the others (Determine 1). Y2 generated and submitted SBOMs in each format their instrument supported (i.e., supply and binary evaluation in addition to enriched and non-enriched).
Determine 1: SBOMs Submitted per Goal
Evaluation
To make sure an goal evaluation, we first decided analysis standards for our assessment of the SBOMs. We then decided automated approaches to extract data from the SBOMs to facilitate our improvement of software program instruments for evaluation in addition to our technology of baseline SBOMs, which we used for comparability functions.
Analysis Standards
Assessing the consistency of the minimal components of the submitted SBOMs was a essential part in figuring out their completeness and accuracy. A listing of minimal components specifies the baseline SBOMs ought to meet and facilitates data sharing. The standards we used for minimal components are these required for documenting a software program product’s main part and its included elements as outlined in CISA’s Framing Software program Part Transparency: Establishing a Frequent Software program Invoice of Supplies (SBOM):
- SBOM Writer Title
- SBOM Timestamp
- SBOM Kind
- SBOM Major Part
- Part Title
- Part Model String
- Part Provider Title
- Part Cryptographic Hash
- Part Distinctive Identifier
- Part Relationships
- Part License
- Part Copyright Holder
Evaluation Instruments
Because of the many submissions, we developed instruments to automate ingesting and processing SBOMs to gather, collate, and export information about them. Members submitted SBOMs in SPDX and CycloneDX codecs in a wide range of encodings together with JSON, XML, and YML.
We wrote code for processing SBOMs utilizing Python inside Jupyter computational notebooks hosted on an SEI inside Bitbucket repository, which additionally contained a replica of SBOM Plugfest submissions. We used two main notebooks for analyzing SBOM submissions: one for CycloneDX and one for SPDX. We sought to extract the next from every SBOM:
- data associated to the presence or absence of minimal components
- details about software program elements, together with their relationships to 1 one other and with the goal software program
In every pocket book, we collected data from every SBOM by doing the next:
- traversing the listing of SBOM submissions, importing JSON SBOM information, and decoding the JSON information in order that information might be extracted
- extracting minimal components from every SBOM the place the information existed and noting the place information was lacking
- developing a dependency tree based mostly on the dependencies listed in every SBOM (These dependency bushes contained details about software program elements and the kinds of relationships amongst these elements as listed within the SBOM.)
- collating information from every SBOM into two frequent information buildings: one for data associated to minimal components and the opposite for part data
We analyzed the information buildings utilizing Python information science packages, or we exported them as comma separated worth (CSV) information for additional evaluation. We used details about the presence or absence of minimal components to generate abstract statistics for every software program goal and every SBOM kind (supply/construct). We used dependency graph data to research the presence/absence of elements and assess the depth of the SBOMs.
Baseline SBOMs
We chosen three outstanding open supply instruments, Syft, Trivy, and Microsoft’s SBOM Software, to create baseline SBOMs for every of the 9 software program targets. The baseline SBOMs served as preliminary examples of what we would count on to see submitted by Plugfest contributors. The baseline SBOMs additionally allowed us to develop evaluation instruments early within the mission so we might begin analyzing contributors’ SBOMs as quickly as they have been submitted.
Findings from SBOM Evaluation
The next are notable findings from our analysis on the SBOMs submitted for the Plugfest. These findings, ordered from the trivial to the extra complicated, clarify the kinds of variances within the SBOMs in addition to their causes.
- Part quantity, content material, and normalization. We discovered important variance in each the variety of elements and the content material of the minimal required components in SBOMs from completely different contributors for a similar software program on the similar lifecycle part. Some variance in SBOM content material is because of the lack of normalization; the identical content material was merely being written otherwise (e.g., software program model detailed as v 2.0 or simply 2.0).
- Software program variations. One other trigger for variance in SBOM content material is that some software program specs enable for a spread of attainable software program variations, however SBOMs enable solely a single model to be documented for every dependency. This leads to SBOMs having varied variations listed throughout completely different contributors for every goal that allowed model ranges.
- Minimal components. Some variance in SBOM content material is because of variations in whether or not contributors included minimal components or not, which can be because of the considerably synthetic nature of producing SBOMs for a analysis mission.
- Use circumstances. SBOMs have numerous use circumstances, which result in various kinds of SBOMs. The wide range of attainable use circumstances is an extra trigger for the dearth of harmonization throughout SBOMs for a similar goal. If we had specified a use case, contributors could have taken a extra harmonized strategy to how they generated, enriched, or augmented their SBOMs for that use case.
- Construct and supply SBOMs. Members used completely different approaches to generate their construct and supply SBOMs, which led to variations within the found elements. Some contributors used a container construct course of to generate their construct SBOM, and others constructed a standalone executable for his or her chosen runtime surroundings utilizing the goal’s language or build-framework-specific course of. Construct SBOMs additionally various based mostly on the surroundings and gear configurations every participant used. Supply SBOMs seize dependencies declared or inferred from supply code. Some contributors used further data from exterior areas, such because the artifact repositories referenced by dependencies or the contents of platform toolchain libraries, to deduce further dependencies.
- Dependency interpretation. A assessment of submitted explanatory readme information and discussions with contributors indicated some variations within the interpretation of dependency. Some submissions included dependencies of first-party elements that aren’t usually deployed, equivalent to goal documentation construct instruments, CI/CD pipeline elements, and elective language bindings.
7 Suggestions for Bettering SBOM High quality
The next suggestions based mostly on our analysis and evaluation will enhance the standard of SBOMs and assist guarantee constant content material in SBOMs for a similar goal.
-
Emphasize inclusion of the next minimal components:-
SBOM Kind.
Embody the SBOM Kind to doc the lifecycle part for which this SBOM was generated (e.g., Supply, Construct). We advocate that this attribute be required reasonably than elective. -
Part Model String.
Emphasize the significance of reporting the model precisely as offered by the provider. This reporting minimizes the necessity for normalization because of information being inconsistently reported (e.g., one SBOM experiences
v 2.0
and one other experiences
2.0
). -
Part Provider Title.
Embody the title of the entity that offered the contents of the software program being described. This helps customers of the SBOM perceive which third events have been a part of the provision chain. A typical registry of part suppliers would assist normalize this entry. For open supply software program elements, which shouldn’t have a standard provider, a direct reference or hyperlink to the mission repository needs to be offered. -
Part Cryptographic Hash.
SBOM steering ought to clearly state what elements are being hashed when a cryptographic hash is included. Make it extra simple for SBOM customers to know tips on how to confirm the hash worth. Alternatively, when supplying cryptographic hashes, SBOM creators needs to be specific about what was hashed. -
Part License.
Emphasize the necessity to present licensing data or to notice that the license data just isn’t recognized or was not included.
-
-
Enhance normalization of SBOM components.
A lot divergence in SBOMs is because of lack of normalization (e.g., model numbering as talked about earlier or
date/time
which can be written as 2025-06-15 or just as August 2025). Standardize on utilizing the time period
provider
for a
main provider
and the time period
producer
for a
secondary provider
. -
Doc how the time period
dependencies
is interpreted within the SBOM technology course of.
Develop steering to tell apart dependencies by class (e.g., runtime, assessments, docs). -
SBOM turbines ought to doc their strategy to producing SBOMs.
This can assist customers higher perceive potential variations in SBOMs for a similar software program. Additionally doc the use case for which the SBOM is being generated. Completely different use circumstances could require variations in SBOMs. -
Use the suitable instrument for the surroundings.
SBOM creators and customers ought to guarantee they’re utilizing an acceptable SBOM instrument for his or her particular surroundings. SBOM instruments usually concentrate on a subset of the programming languages and construct environments. -
Assist developer neighborhood SBOM efforts.
Some developer communities are working to incorporate SBOM turbines in language instruments and construct frameworks to make it a lot simpler for initiatives utilizing these languages and frameworks to generate SBOMs as upstream suppliers. These efforts have an outsize impression as a result of they decrease the barrier for creating SBOMs and push the SBOM technology additional upstream to mission maintainers who’ve detailed data of their very own supply code and construct processes. -
Develop and validate SBOM profiles.
To assist stakeholders talk extra successfully, they might develop and validate SBOM profiles, every profile being a well-defined restriction positioned on a number of SBOM requirements to make clear that means and allowable values for every discipline, its cardinality, and structural features. The
OWASP Software program Part Verifications Commonplace (SCVS) BOM Maturity Mannequin
profiles function is an instance. One other strategy could be to outline a JSON schema that extends the prevailing schemas for CycloneDX and/or SPDX and provides the mandatory clarifications and restrictions for a profile.
Future Work on Making certain SBOM High quality
SBOMs are of rising significance to safeguarding the safety of all software program programs, together with DoD and demanding infrastructure programs. As extra organizations require use of SBOMs, there might be higher want to make sure their high quality and completeness, together with offering transparency for undeclared dependencies. Choices to maintain SBOM components opaque could also be rethought if third celebration SBOMs can present wanted transparency. This analysis mission is a part of a seamless SEI effort to enhance the standard of SBOMs.