# MAL-2026-12616: Malicious code in claims-format-date (npm)


- **Type:** Malicious package
- **Package:** `claims-format-date` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12616?

MAL-2026-12616 is a malicious package in claims-format-date, published on 5 Aug 2026. 

### Official description

claims-format-date@35.6.5 auto-executes a binary dropper when the module is required. index.js requires./_init on load; _init.js downloads a platform-specific binary from string-split-obfuscated Cloudflare Workers hosts (oob-worker.cf102-baf.workers.dev, oob-worker.cf100-416.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf99-9b3.workers.dev) with a DNS TXT base64-chunk fallback through sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru. The fetched bytes are written to /tmp or %TEMP% under disguised names (.cache_<uid>, dotnet_diag_<uid>.exe), chmod 0755, and detached-spawned via /bin/sh -c or cmd.exe /c start /b. Hostnames and sensitive API references are reconstructed at runtime through array joins and string concatenation (require("child_"+"process"), fs["chmod"+"Sync"]) to evade static analysis. A second parallel dropper implementation in lib/telemetry.js decodes a base64 buffer and performs the same write/chmod/exec chain under an 'analytics SDK' cover story. The package name resembles common date-formatting utilities but the shipped code implements remote payload execution on require.

## What should I do about MAL-2026-12616?

Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.

## Fix prompt for AI coding agents

```text
MAL-2026-12616 is a malicious package: claims-format-date (npm). Every version was published to cause harm.

Task:
1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.
2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.
3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.
4. If the package is not used anywhere, say so and change nothing.

Reference: https://insights.sbomify.com/MAL-2026-12616/ (Markdown: https://insights.sbomify.com/MAL-2026-12616/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12616

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12616/
Summaries are generated and may contain mistakes; the official description above is the record.