CVE-2026-40556
Insecure Directory Permissions in GNU nano Leading to Privilege Abuse
Description
GNU nano creates the user’s ~/.local directory with overly permissive permissions when the directory does not exist yet. On first use of features requiring Cross-Desktop Group (XDG) data storage, nano explicitly requests directory mode 0777, making the directory world‑writable in environments where the process umask does not sufficiently restrict permissions. In systems with a relaxed or zero umask, such as container environments, CI/CD runners, embedded systems, or user shells configured with umask 000, this results in ~/.local being created as world‑writable. A local attacker can exploit a race window between nano’s creation of ~/.local and its subsequent creation of more restrictive subdirectories to write attacker‑controlled files into the victim’s XDG directory hierarchy. This problem was fixed in nano version 9.0
INFO
Published Date :
April 28, 2026, 3:16 p.m.
Last Modified :
April 28, 2026, 3:16 p.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-40556
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | LOW | 4bb8329e-dd38-46c1-aafb-9bf32bcb93c6 | ||||
| CVSS 4.0 | LOW | [email protected] |
Solution
- Update nano to version 9.0 or higher.
- Verify and correct ~/.local directory permissions.
- Ensure restrictive umask settings are applied.
- Review container and CI/CD configurations.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40556.
| URL | Resource |
|---|---|
| https://cert.pl/en/posts/2026/04/CVE-2026-40556/ | |
| https://cgit.git.savannah.gnu.org/cgit/nano.git/commit/?id=cb43493e | |
| https://www.nano-editor.org/ |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40556 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40556
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40556 vulnerability anywhere in the article.
-
cert.pl
Vulnerability in GNU nano software
Vulnerability in GNU nano software CVE ID CVE-2026-40556 Publication date 28 April 2026 Vendor GNU Product nano Vulnerable versions From 2.9.1 below 9.0 Vulnerability type (CWE) Incorrect Permission A ... Read more
The following table lists the changes that have been made to the
CVE-2026-40556 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Apr. 28, 2026
Action Type Old Value New Value Added Description GNU nano creates the user’s ~/.local directory with overly permissive permissions when the directory does not exist yet. On first use of features requiring Cross-Desktop Group (XDG) data storage, nano explicitly requests directory mode 0777, making the directory world‑writable in environments where the process umask does not sufficiently restrict permissions. In systems with a relaxed or zero umask, such as container environments, CI/CD runners, embedded systems, or user shells configured with umask 000, this results in ~/.local being created as world‑writable. A local attacker can exploit a race window between nano’s creation of ~/.local and its subsequent creation of more restrictive subdirectories to write attacker‑controlled files into the victim’s XDG directory hierarchy. This problem was fixed in nano version 9.0 Added CVSS V4.0 AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-732 Added Reference https://cert.pl/en/posts/2026/04/CVE-2026-40556/ Added Reference https://cgit.git.savannah.gnu.org/cgit/nano.git/commit/?id=cb43493e Added Reference https://www.nano-editor.org/