`cut` routes `-z -d ''` through a special newline-delimiter path that ignores the `-s` only-delimited flag, emitting whole undelimited records (plus NUL) that should be suppressed. Pipelines relying on `cut -s` to drop undelimited records process data that should be filtered.
```
printf 'abc' | cut -z -d '' -s -f 1 | od -An -tx1 # GNU: no output ; uutils: 61 62 63 00
```
---
_Zellic private finding (zellic-ext/coreutils-private PR #102). Reported in the Zellic *uutils coreutils Program Security Assessment* (for Canonical, Jan 2026), audited commit `3a07ffc5a9bd4c283e75afa548ba1f1957bad242`._
A logic error in the cut utility of uutils coreutils causes the program to incorrectly interpret the literal two-byte string '' (two single quotes) as an empty delimiter. The implementation mistakenly maps this string to the NUL character for both the -d (delimiter) and --output-delimiter options. This vulnerability can lead to silent data corruption or logic errors in automated scripts and data pipelines that process strings containing these characters, as the utility may unintentionally split or join data on NUL bytes rather than the intended literal characters.
A logic error in the tr utility of uutils coreutils causes the program to incorrectly define the [:graph:] and [:print:] character classes. The implementation mistakenly includes the ASCII space character (0x20) in the [:graph:] class and excludes it from the [:print:] class, effectively reversing the standard behavior established by POSIX and GNU coreutils. This vulnerability leads to unintended data modification or loss when the utility is used in automated scripts or data-cleaning pipelines that rely on standard character class semantics. For example, a command executed to delete all graphical characters while intending to preserve whitespace will incorrectly delete all ASCII spaces, potentially resulting in data corruption or logic failures in downstream processing.
A logic error in the expr utility of uutils coreutils causes the program to evaluate parenthesized subexpressions during the parsing phase rather than at the execution phase. This implementation flaw prevents the utility from performing proper short-circuiting for logical OR (|) and AND (&) operations. As a result, arithmetic errors (such as division by zero) occurring within "dead" branches, branches that should be ignored due to short-circuiting, are raised as fatal errors. This divergence from GNU expr behavior can cause guarded expressions within shell scripts to fail with hard errors instead of returning expected boolean results, leading to premature script termination and breaking GNU-compatible shell control flow.
A logic error in the env utility of uutils coreutils causes a failure to correctly parse command-line arguments when utilizing the -S (split-string) option. In GNU env, backslashes within single quotes are treated literally (with the exceptions of \\ and \'). However, the uutils implementation incorrectly attempts to validate these sequences, resulting in an "invalid sequence" error and an immediate process termination with an exit status of 125 when encountering valid but unrecognized sequences like \a or \x. This divergence from GNU behavior breaks compatibility for automated scripts and administrative workflows that rely on standard split-string semantics, leading to a local denial of service for those operations.
A Time-of-Check to Time-of-Use (TOCTOU) vulnerability exists in the chcon utility of uutils coreutils during recursive operations. The implementation resolves recursive targets using a fresh path lookup (via fts_accpath) rather than binding the traversal and label application to the specific directory state encountered during traversal. Because these operations are not anchored to file descriptors, a local attacker with write access to a directory tree can exploit timing-sensitive rename or symbolic link races to redirect a privileged recursive relabeling operation to unintended files or directories. This vulnerability breaks the hardening expectations for SELinux administration workflows and can lead to the unauthorized modification of security labels on sensitive system objects.
A logic error in the split utility of uutils coreutils causes the corruption of output filenames when provided with non-UTF-8 prefix or suffix inputs. The implementation utilizes to_string_lossy() when constructing chunk filenames, which automatically rewrites invalid byte sequences into the UTF-8 replacement character (U+FFFD). This behavior diverges from GNU split, which preserves raw pathname bytes intact. In environments utilizing non-UTF-8 encodings, this vulnerability leads to the creation of files with incorrect names, potentially causing filename collisions, broken automation, or the misdirection of output data.
A Time-of-Check to Time-of-Use (TOCTOU) vulnerability exists in the split utility of uutils coreutils. The program attempts to prevent data loss by checking for identity between input and output files using their file paths before initiating the split operation. However, the utility subsequently opens the output file with truncation after this path-based validation is complete. A local attacker with write access to the directory can exploit this race window by manipulating mutable path components (e.g., swapping a path with a symbolic link). This can cause split to truncate and write to an unintended target file, potentially including the input file itself or other sensitive files accessible to the process, leading to permanent data loss.
A logic error in the ln utility of uutils coreutils causes it to reject source paths containing non-UTF-8 filename bytes when using target-directory forms. Unlike GNU ln, which treats filenames as raw bytes, uutils coreutils enforces UTF-8 encoding, leading to failure to stat such files and a non-zero exit code. This behavior can cause local denial of service in environments with valid non-UTF-8 filenames.
A logic error in the ln utility of uutils coreutils allows the utility to dereference a symbolic link target even when the --no-dereference (or -n) flag is explicitly provided. The implementation previously only honored the "no-dereference" intent if the --force (overwrite) mode was also enabled. This flaw causes ln to follow a symbolic link that points to a directory and create new links inside that target directory instead of treating the symbolic link itself as the destination. In environments where a privileged user or system script uses ln -n to update a symlink, a local attacker could manipulate existing symbolic links to redirect file creation into sensitive directories, potentially leading to unauthorized file creation or system misconfiguration.
CVE-2026-35371 is a low-severity vulnerability in the id utility of uutils coreutils where the "pretty print" output misrepresents the effective user information. The utility incorrectly uses the effective group ID (GID) instead of the effective user ID (UID) when performing a name lookup for the effective user. This causes misleading diagnostic output that may lead to incorrect decisions about file permissions or access control by automated scripts or system administrators.
CVE-2026-35370 is a medium severity vulnerability in the id utility of uutils coreutils where the groups= output section is incorrectly calculated using the user's real GID instead of the effective GID. This causes the output to diverge from GNU coreutils, potentially misleading scripts and automated processes that rely on this output for security-critical access control decisions. The discrepancy may lead to unauthorized access or security misconfigurations.
A vulnerability in the kill utility of uutils coreutils causes improper input validation. The utility misinterprets the argument 'kill -1' as a request to send the default signal (SIGTERM) to PID -1, which causes the kernel to terminate all processes visible to the caller. This behavior differs from GNU coreutils, which correctly treats '-1' as a signal number and reports a missing PID argument. This can lead to a system crash or massive process termination.
A vulnerability exists in the chroot utility of uutils coreutils when using the --userspec option. The utility resolves the user specification via getpwnam() after entering the chroot but before dropping root privileges. On glibc-based systems, this can trigger the Name Service Switch (NSS) to load shared libraries (e.g., libnss_*.so.2) from the new root directory. If the NEWROOT is writable by an attacker, they can inject a malicious NSS module to execute arbitrary code as root, facilitating a full container escape or privilege escalation.
The nohup utility in uutils coreutils creates its default output file, nohup.out, without specifying explicit restricted permissions. This causes the file to inherit umask-based permissions, typically resulting in a world-readable file (0644). In multi-user environments, this allows any user on the system to read the captured stdout/stderr output of a command, potentially exposing sensitive information. This behavior diverges from GNU coreutils, which creates nohup.out with owner-only (0600) permissions.
The printenv utility in uutils coreutils does not display environment variables containing invalid UTF-8 byte sequences, silently skipping them instead. This behavior deviates from POSIX standards, which allow arbitrary bytes in environment strings. As a result, malicious environment variables with invalid UTF-8 can evade inspection by administrators or security tools, potentially hiding attacks such as library injection. The vulnerability affects version 0 of uutils coreutils and has a medium severity rating with a CVSS score of 4.4.
The mv utility in uutils coreutils improperly handles symbolic links when moving directory trees across filesystem boundaries by expanding symlinks instead of preserving them. This behavior can cause resource exhaustion, unexpected duplication of sensitive data, or infinite recursion due to symlink loops. The vulnerability is tracked as CVE-2026-35365 with a medium severity rating and a CVSS score of 6.6. No patch or official remediation has been confirmed yet.
A Time-of-Check to Time-of-Use (TOCTOU) race condition exists in the mv utility of uutils coreutils during cross-device operations. The utility removes the destination path before recreating it through a copy operation. A local attacker with write access to the destination directory can exploit this window to replace the destination with a symbolic link. The subsequent privileged move operation will follow the symlink, allowing the attacker to redirect the write and overwrite an arbitrary target file with contents from the source.
CVE-2026-35363 is a path traversal vulnerability in the rm utility of uutils coreutils. The utility is intended to prevent deletion of the current directory by refusing to delete . or .., but it fails to recognize equivalent paths with trailing slashes such as ./ or .///. This flaw allows an execution of rm -rf ./ to recursively delete all contents within the current directory silently. The command misleadingly reports an 'Invalid input' error, potentially causing users to overlook the data loss. The vulnerability has a medium severity with a CVSS score of 5.6.
A TOCTOU (Time-of-Check to Time-of-Use) race condition exists in the safe_traversal module of uutils coreutils. This module uses file-descriptor-relative syscalls to protect against symlink race conditions but only on Linux systems. On other Unix-like systems such as macOS and FreeBSD, these protections are not applied, leaving directory traversal vulnerable to symlink race attacks. The vulnerability has a low severity score and currently no known exploits or patches.