{"answers":{"affected":"1 open source package ship an affected version, including birch-css-utils.","exploited":"There is no known exploitation of MAL-2026-18331 in the wild and no public exploit code.","fix":"Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.","what":"MAL-2026-18331 is a malicious package in birch-css-utils, published on 26 Oct 2026."},"fix_prompt":"MAL-2026-18331 is a malicious package: birch-css-utils (npm). Every version was published to cause harm.\n\nTask:\n1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.\n2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.\n3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.\n4. If the package is not used anywhere, say so and change nothing.\n\nReference: https://insights.sbomify.com/MAL-2026-18331/ (Markdown: https://insights.sbomify.com/MAL-2026-18331/index.md)","id":"MAL-2026-18331","markdown":"https://insights.sbomify.com/MAL-2026-18331/index.md","name":"MAL-2026-18331","record":{"aliases":["GHSA-p597-2ggw-c82r"],"analysis":null,"analysis_generated_by":null,"assigner":null,"cpe":[],"cvss":{"score":null,"severity":null,"source":null,"vector":null,"version":null},"cwes":[],"description":"Package advertises itself as a zero-runtime CSS theme kit and instructs installation as a Tailwind name-overlay (`npm install -D tailwindcss@npm:birch-css-utils`), but the published tarball contains ~760KB of heavily obfuscated JS (`build-cache.mjs`, `cache-sweep.mjs`, `cache-warm.mjs`) hidden behind a `tailwindcss-theme-kit build cache manifest` cover comment. The declared `./tokens` export (`tokens.mjs`) top-level-imports `cache-warm.mjs`, so consumers that import `birch-css-utils/tokens` execute the obfuscated code on module load. The bundles use a hex-named XOR-encoded string array; decoding with key 0xED reveals AWS Sigv4 signing primitives (`AWS4-HMAC-SHA256#Credential=`), an AWS Access Key ID regex (`^(?:AKIA|ASIA|ABIA|ACCA)[A-Z0-9]{16}$`), and git identity env var names (`GIT_AUTHOR_NAME`, `GIT_AUTHOR_DATE`) embedded in the string array. A CSS custom-properties package has no legitimate use for AWS v4 signing material or an AWS key-ID matcher. The combination of Tailwind name-overlay install instructions, a README denying runtime JS, obfuscated executable bundles reachable from a public export, and decoded AWS credential-harvesting primitives constitutes a Tailwind imposter that steals AWS credentials from importing consumers.\n\nAny computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.","ecosystems":["npm"],"exploits":{"exploitdb":null,"first_seen":null,"github_poc":null,"max_poc_stars":null,"metasploit":null,"nuclei":null,"refs":[],"tier":null},"has_fix":false,"headline":"Malicious code in birch-css-utils (npm)","id":"MAL-2026-18331","indexable":true,"kev":null,"kind":"malicious","links":{"ecosystem":"npm","product":null,"products":[],"type":null,"year":"2026"},"n_packages":1,"n_references":null,"packages":[{"ecosystem":"npm","fixed":[],"introduced":["0"],"last_affected":[],"package":"birch-css-utils","purl":"pkg:npm/birch-css-utils","source":"MAL-2026-18331"}],"products":null,"published":"2026-10-26","related":[],"sources":[{"class":"attribution","licence":"Apache-2.0","name":"OpenSSF Malicious Packages","prefix":"MAL"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":null,"updated":null,"vendors":null},"summary":null,"url":"https://insights.sbomify.com/MAL-2026-18331/"}