CyberSecBulletin
CVE-2026-39822NVD status: Analyzed

os: UNIX Symbolic Link (Symlink) Following

Published Updated By the CyberSecBulletin desk

CVE-2026-39822 is a high-severity UNIX symbolic link (symlink) following vulnerability in os from Go standard library, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 1.25.12, 1.26.5, 1.27.0-rc.2 as the first without the flaw, so updating os to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.23% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update os to 1.25.12 or 1.26.5 or 1.27.0-rc.2, whichever matches your release line, or a later version.
  2. Update Go to 1.25.12 or 1.26.5, whichever matches your release line, or a later version.
  3. Read the advisory on groups.google.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
Go standard libraryosbefore 1.25.12; 1.26.0-0 up to, but not including, 1.26.5; 1.27.0-0 up to, but not including, 1.27.0-rc.21.25.12, 1.26.5, 1.27.0-rc.2
GoGo1.24.0 up to, but not including, 1.25.12; 1.26.0 up to, but not including, 1.26.5; 1.271.25.12, 1.26.5

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: 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 developers prevent this class of flaw

  • 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.
  • 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.

More UNIX Symbolic Link (Symlink) Following vulnerabilities (CWE-61)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Other vulnerabilities in os

All os vulnerabilities

Recent UNIX Symbolic Link (Symlink) Following vulnerabilities

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