CVE-2026-121549

The nnn file manager through 5.3 contains an insecure file handling vulnerability allowing local attackers to redirect writes because main() accepts an existing NNN_FIFO path without verifying it is a FIFO. Attackers can pre-create the predictable /tmp/nnn.fifo path as a symlink or readable regular file, causing victim-writable files to be overwritten or leaking the victim's browsed paths.

nnn does not sanitize the filename variable. An attacker can place a file with a crafted name on a shared filesystem, removable media, or inside an extracted archive whose name contains a single quote followed by shell syntax. If the victim navigates to that file and opens it with preview-tabbed, the filename is embedded into the generated shell command and the injected payload executes with the privileges of the nnn process. Maintainer of this project was notified about this vulnerability. It might has been addressed, but the maintainer did not provide a vulnerable version range. Only version 5.2 was tested and confirmed as vulnerable.

nnn does not sanitize the path variable. An attacker can create a directory on a shared filesystem, removable media, or inside an extracted archive whose name contains a single quote followed by shell syntax. If the victim enters that directory in nnn and uses the batch copy or move workflow, the crafted directory name is embedded into the generated shell command and the injected payload executes with the privileges of the nnn process. Maintainer of this project was notified about this vulnerability. It might has been addressed, but the maintainer did not provide a vulnerable version range. Only version 5.2 was tested and confirmed as vulnerable.

nnn stores homelen variable as uchar_t, which can only represent values in the range 0-255. An attacker who can influence the victim's execution environment can provide an arbitrary HOME path with length that is truncated to 0. The expression (homelen - 1) is promoted to signed int and becomes -1, producing an out-of-bounds read and an out-of-bounds write one byte before the path buffer. Only version 5.2 was tested and confirmed as vulnerable.

nnn is vulnerable to an out-of-bounds write vulnerability. Due to lack of validation of attacker-controlled length fields deserialized from a session file, a crafted session file can cause nnn to write data beyond the bounds of fixed-size global buffers when loaded with the -s option. An attacker who can place a malicious session file in the victim's nnn session directory can exploit this to corrupt adjacent global state. Only version 5.2 was tested and confirmed as vulnerable.