GO-2026-4970 BIT-golang-2026-39822 CVE-2026-39822
Root escape via symlink plus trailing slash in os
- Severity
- 7.8 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.23%
- Chance of exploitation in the next 30 days. Higher than 14.18% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-61 UNIX Symbolic Link (Symlink) Following
- Fix
1.27.0-rc.2- Upgrade stdlib to this version or later
Description
On Unix systems, opening a file in an os.Root improperly follows symlinks to locations outside of the Root when the final path component of the a path is a symbolic link and the path ends in /.
For example, 'root.Open("symlink/")' will open "symlink" even when "symlink" is a symbolic link pointing outside of the root.
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| stdlib | < 1.25.12>= 1.26.0-0, < 1.26.5>= 1.27.0-0, < 1.27.0-rc.2 |
1.25.121.26.51.27.0-rc.2 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
stdlib Go → 1.27.0-rc.2
- go
go get stdlib@v1.27.0-rc.2 && go mod tidy
Severity breakdown
CVSS 3.1 7.8
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Weakness
CWE-61: UNIX Symbolic Link (Symlink) Following
The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
How to prevent it
- Implementation: Symbolic link attacks often occur when a program creates a tmp directory that stores files/links. Access to the directory should be restricted to the program as to prevent attackers from manipulating the files.
- Architecture and Design: Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
References
Advisories
Fixes and patches
Issue reports
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-4374-p667-p6c8 HTTP/2 rapid reset can cause excessive work in net/http | High Known exploited | Also affects stdlib |
| CVE-2020-0601 Certificate validation bypass on Windows in crypto/x509 | High Known exploited | Also affects stdlib |
| RUSTSEC-2026-0382 Distrust compromised intermediate certificates in crypto/x509 | Medium | Also affects stdlib |
| GO-2026-6613 HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http | High | Also affects stdlib |
| GO-2026-6609 Lack of limit on size of parsed Range headers in net/http | High | Also affects stdlib |
| GO-2026-6608 Memory limit bypass when parsing MIME headers in net/textproto, mime/multipart | High | Also affects stdlib |
| GO-2026-6607 Reject malformed ECH outer extension references in crypto/tls | High | Also affects stdlib |
| GO-2026-6604 Root.Mkdir(All) can follow junctions out of the root on Windows in os | Critical | Also affects stdlib |
Credits: Mundur (https://github.com/M0nd0R)
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