CVE-2026-40556
What is CVE-2026-40556?
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
FAQ
CVE-2026-40556 has a CVSS score of N/A/10, rated as Unknown. Review the affected products list and apply vendor patches.
CVSS (Common Vulnerability Scoring System) rates vulnerability severity from 0.0 to 10.0. CVE-2026-40556 scores N/A/10 (Unknown). Scores 9.0–10.0 are Critical, 7.0–8.9 are High, 4.0–6.9 are Medium, and below 4.0 are Low.
The list of devices confirmed to be affected by CVE-2026-40556 is shown in the "Affected Devices" section above. Check your firmware version against the vendor security advisory and apply the latest patch.
Apply the latest firmware or software update from the vendor. Check the References section above for official advisories and patch notes. If no patch is available, consider disabling the affected feature or isolating the device from untrusted networks.