GO-2026-4864 BIT-golang-2026-32282 CVE-2026-32282
TOCTOU permits root escape on Linux via Root.Chmod in os in internal/syscall/unix
- Severity
- 6.4 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.29%
- Chance of exploitation in the next 30 days. Higher than 21.77% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-59 Improper Link Resolution Before File Access ('Link Following')
- Fix
1.26.2- Upgrade stdlib to this version or later
Description
On Linux, if the target of Root.Chmod is replaced with a symlink while the chmod operation is in progress, Chmod can operate on the target of the symlink, even when the target lies outside the root.
The Linux fchmodat syscall silently ignores the AT_SYMLINK_NOFOLLOW flag, which Root.Chmod uses to avoid symlink traversal. Root.Chmod checks its target before acting and returns an error if the target is a symlink lying outside the root, so the impact is limited to cases where the target is replaced with a symlink between the check and operation.
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| stdlib | < 1.25.9>= 1.26.0-0, < 1.26.2 |
1.25.91.26.2 |
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 → 1.26.2
- go
go get stdlib@v1.26.2 && go mod tidy
Severity breakdown
CVSS 3.1 6.4
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
- Attack vector
- Local
- Attack complexity
- High
- Privileges required
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Weakness
CWE-59: Improper Link Resolution Before File Access ('Link Following')
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
How to prevent it
- 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: Uuganbayar Lkhamsuren (https://github.com/uug4na)
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