CVE-2026-49356

@babel/core: Arbitrary File Read via sourceMappingURL Comment

Workarounds

Callers can mitigate the issue without upgrading by setting inputSourceMap: false in their Babel options.

Callers can also manually extract the #sourceMappingURL comment from the input source code, validate whether the source map that it links to is allowed to be read, and if it is pass an object to inputSourceMap (passing false when it's not).

Credits

Thanks Teodor-Cristian Radoi for reporting the vulnerability.

Using @babel/core to compile maliciously crafted code can allow ab attacker to read any source map from the system that is running Babel, if these conditions are all true:

• the attacker controls the input source code
• the attacker can read the output source code
• the attacker knows the path of the source map file that they want to read

Users that only compile trusted code are not impacted.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-49356 has a CVSS score of 3.2 (Low). The vector is requires local access, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (8.0.0-rc.6, 7.29.6); upgrading removes the vulnerable code path.

Kodem intelligence

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The vulnerability has been fixed in @babel/[email protected] and @babel/[email protected].

1. What is CVE-2026-49356? CVE-2026-49356 is a low-severity path traversal vulnerability in @babel/core (npm), affecting versions >= 8.0.0-alpha.0, < 8.0.0-rc.5. It is fixed in 8.0.0-rc.6, 7.29.6. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-49356? CVE-2026-49356 has a CVSS score of 3.2 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @babel/core are affected by CVE-2026-49356? @babel/core (npm) versions >= 8.0.0-alpha.0, < 8.0.0-rc.5 is affected.
4. Is there a fix for CVE-2026-49356? Yes. CVE-2026-49356 is fixed in 8.0.0-rc.6, 7.29.6. Upgrade to this version or later.
5. Is CVE-2026-49356 exploitable, and should I be worried? Whether CVE-2026-49356 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-49356 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-49356?
   • Upgrade @babel/core to 8.0.0-rc.6 or later
   • Upgrade @babel/core to 7.29.6 or later