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A University of Toronto computing administrator says Ubuntu 26.04’s Rust-based sudo, sudo-rs, did not honor an existing sudoers rule using wildcard command arguments. The sudo-rs manual documents that command-line argument wildcards are unsupported, meaning some standard sudo configurations may not work as administrators expect; the report describes one installation, not a system-wide investigation.
A University of Toronto computing administrator says Ubuntu 26.04’s Rust-based sudo, sudo-rs, failed to honor an existing /etc/sudoers.d rule that permits certain Exim commands without a password. The reported problem stems from a documented difference: sudo-rs does not support wildcards in command-line arguments in the same way as standard sudo, a compatibility issue that could affect systems carrying over existing sudo policies.
In a report published on November 2, 2026, the administrator said a rule for the corestaff group was intended to allow several specific Exim queue-display options without a password. Under standard sudo, the rule’s pattern was understood to permit commands such as exim -bpa, -bpc, -bpr and -bpu. With sudo-rs, the administrator said, the bracketed pattern was passed as a literal argument instead of matching those options.
The report included an example command and output: running sudo-rs with /usr/sbin/exim “-bp[acru]” produced an Exim error saying the option was unknown, malformed or incomplete. The administrator also said the rule appeared not to be applied and that they saw no logging about the failure. This is an account from one administrator; the report does not establish how often the behavior occurs or whether other configurations are affected.
The sudo-rs manual page describes the limitation in its discussion of wildcards. According to the text quoted in the report, wildcards in command-line arguments are unsupported, apart from a final asterisk that can represent zero or more subsequent arguments. The administrator said they switched the affected machines to /usr/bin/sudo.ws using update-alternatives. They also said their installation framework now disables sudo-rs alongside Rust coreutils.
Existing sudo Rules May Behave Differently
The report highlights a practical migration risk for administrators: sudo policy files can depend on command-matching behavior, and a replacement implementation may interpret those rules differently. If an existing rule no longer matches, a permitted command may fail, disrupting routine administration or automation. The reported example concerned an Exim command, but the underlying issue is the difference in how command-line argument wildcards are handled.
That does not establish that sudo-rs is broadly unsafe or that every Ubuntu 26.04 installation will encounter a problem. It does mean administrators should not assume that a policy accepted by standard sudo will work identically under sudo-rs. The account also raises a documentation concern: the author argues the compatibility difference is easy to miss while reading the manual. Clear notice of behavioral differences can help teams review policies before relying on a new implementation.
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The Rule and Its Replacement
The report concerns sudo-rs, a Rust implementation of sudo used on the author’s Ubuntu 26.04 machines. Sudo lets administrators define which commands users may run with elevated privileges; sudoers files can specify users or groups, commands and password requirements. Administrators often maintain additional rules in /etc/sudoers.d, as the author did.
The specific rule used a bracketed pattern in an Exim command argument. The author says standard sudo treats that pattern as matching the listed single-character options, while sudo-rs treats it as a literal string. The sudo-rs manual, as quoted by the author, explicitly says argument wildcards are not supported and explains that this differs from original sudo. The report does not provide a separate technical investigation or a response from Ubuntu or the sudo-rs developers.
After encountering the failure, the administrator changed the selected sudo implementation to /usr/bin/sudo.ws. They said removing the sudo-rs package outright would also remove ubuntu-minimal, so they did not take that route. Their comments about Canonical’s motivations and possible future use of Debian are the author’s views and plans, not confirmed Ubuntu policy changes.
“Wildcards in command line arguments are not supported.”
— The sudo-rs manual page, as quoted in the report
Scope and Ubuntu Response Remain Unknown
The source is a single administrator’s account and does not include a reproducible test across multiple Ubuntu installations, an independent review, or a response from Canonical or the sudo-rs developers. It is not clear whether the behavior described is expected for all relevant sudo-rs configurations, whether any other part of the rule contributed to the result, or whether a later package update has changed it.
The administrator reports seeing no logging about the rule failure, but the source does not establish whether sudo-rs generally omits logs in such cases or whether logging settings affected this instance. There is also no evidence in the report that the wildcard behavior creates a security vulnerability. The confirmed concern in the account is a compatibility and command-authorization mismatch compared with the author’s expectations under standard sudo.
Administrators May Need Policy Checks
The author says the affected systems have been switched away from sudo-rs through update-alternatives, and their installer framework has been changed to disable it. The report does not identify a planned fix, a developer investigation or a release date for a change.
For other administrators, the immediate practical step is to check whether local sudoers rules rely on wildcard matching in command arguments and compare those rules with the sudo-rs manual’s stated limitations. Whether Canonical or the sudo-rs project will provide further guidance or alter the implementation remains unclear; the source says no bug report was filed.
Key Questions
What failed on the Ubuntu 26.04 system?
The administrator said sudo-rs did not match a sudoers rule containing a wildcard in an Exim command argument. The command received a literal bracketed string and Exim rejected it.
Does sudo-rs support wildcards in command arguments?
According to the manual text quoted in the report, command-line argument wildcards are not supported, with a limited exception for a final asterisk representing subsequent arguments.
Is this a confirmed problem on every Ubuntu 26.04 machine?
No. The source documents one administrator’s experience and does not report testing across other installations or configurations.
What did the administrator do?
The administrator says they selected /usr/bin/sudo.ws with update-alternatives and changed their installer framework to disable sudo-rs. They did not remove the package because doing so would also remove ubuntu-minimal, according to their account.
Has Canonical responded or announced a fix?
The report contains no response from Canonical or the sudo-rs developers and describes no announced fix. The author said they had not filed a bug report.
Source: utcc.utoronto.ca
