/ 
perl-5.42.0
⭐ Starred 2013 / App::Cpan
Security Advisories (5)
CVE-2026-13221 (2026-07-13)

Perl versions through 5.43.9 produce silently incorrect regular expression matches when an alternation of more than 65535 fixed string branches is compiled into a trie in Perl_study_chunk. When such branches are combined into a trie, the delta between the first branch and the shared tail is stored in a 16-bit field. A branch count above 65535 overflows the field, and the trie's match decision table is truncated with no warning or error. A pattern of this shape produces false positive matches (matching strings it should not) and false negative matches (failing to match strings it should). When such a pattern gates an access or filtering decision, the result is wrong.

CVE-2026-15534 (2026-08-09)

Perl versions through 5.45.1 have out-of-bounds heap reads and writes during regular expression matching via an undersized superlinear cache in S_regmatch. The regex engine's superlinear cache holds one bit per subject position for each participating WHILEM node, so the bit count is the subject length plus one times the number of nodes. Nothing checks that product for positive overflow of the signed 32-bit count: a 286331153 byte subject matched against a pattern with 15 participating nodes stores the count as 14, leaving a two byte cache. The cache is then indexed from the real match position and node number, so reads go past the end of the allocation, and on failure CACHEsayNO sets a bit past it. A caller that matches an attacker controlled subject of this size against a pattern of this shape can crash the process or corrupt heap memory.

CVE-2026-8376 (2026-05-25)

Perl versions through 5.43.10 have a heap buffer overflow when compiling regular expressions with a repeated fixed string on 32-bit builds. Perl_study_chunk in regcomp_study.c checked the size of the joined substring buffer in characters rather than bytes. For a quantified fixed substring with a large minimum count, the byte length mincount * l could overflow SSize_t, producing an undersized SvGROW allocation; the subsequent copy writes past the end of the buffer. A caller that compiles an attacker-controlled regular expression on a 32-bit perl build triggers a heap buffer overflow at compile time.

CVE-2026-4176 (2026-03-29)

Perl versions from 5.9.4 before 5.40.4-RC1, from 5.41.0 before 5.42.2-RC1, from 5.43.0 before 5.43.9 contain a vulnerable version of Compress::Raw::Zlib. Compress::Raw::Zlib is included in the Perl package as a dual-life core module, and is vulnerable to CVE-2026-3381 due to a vendored version of zlib which has several vulnerabilities, including CVE-2026-27171. The bundled Compress::Raw::Zlib was updated to version 2.221 in Perl blead commit c75ae9cc164205e1b6d6dbd57bd2c65c8593fe94.

CVE-2026-57432 (2026-07-13)

Perl versions through 5.43.10 have an integer overflow in S_measure_struct leading to an out-of-bounds heap read in pack and unpack. S_measure_struct adds each item's size times its repeat count to a running total with no overflow check, so a large repeat count in a pack or unpack template wraps the signed SSize_t total negative. The @, X, and x position codes then guard their moves with a signed length comparison that passes when the length is negative, advancing the buffer pointer out of bounds. A template derived from untrusted input can read heap memory past the buffer and return it to the caller.

NAME

App::Cpan - easily interact with CPAN from the command line

SYNOPSIS

# with arguments and no switches, installs specified modules
cpan module_name [ module_name ... ]

# with switches, installs modules with extra behavior
cpan [-cfFimtTw] module_name [ module_name ... ]

# use local::lib
cpan -I module_name [ module_name ... ]

# one time mirror override for faster mirrors
cpan -p ...

# with just the dot, install from the distribution in the
# current directory
cpan .

# without arguments, starts CPAN.pm shell
cpan

# without arguments, but some switches
cpan [-ahpruvACDLOPX]

DESCRIPTION

This script provides a command interface (not a shell) to CPAN. At the moment it uses CPAN.pm to do the work, but it is not a one-shot command runner for CPAN.pm.

Options

-a

Creates a CPAN.pm autobundle with CPAN::Shell->autobundle.

-A module [ module ... ]

Shows the primary maintainers for the specified modules.

-c module

Runs a `make clean` in the specified module's directories.

-C module [ module ... ]

Show the Changes files for the specified modules

-D module [ module ... ]

Show the module details. This prints one line for each out-of-date module (meaning, modules locally installed but have newer versions on CPAN). Each line has three columns: module name, local version, and CPAN version.

-f

Force the specified action, when it normally would have failed. Use this to install a module even if its tests fail. When you use this option, -i is not optional for installing a module when you need to force it:

% cpan -f -i Module::Foo
-F

Turn off CPAN.pm's attempts to lock anything. You should be careful with this since you might end up with multiple scripts trying to muck in the same directory. This isn't so much of a concern if you're loading a special config with -j, and that config sets up its own work directories.

-g module [ module ... ]

Downloads to the current directory the latest distribution of the module.

-G module [ module ... ]

UNIMPLEMENTED

Download to the current directory the latest distribution of the modules, unpack each distribution, and create a git repository for each distribution.

If you want this feature, check out Yanick Champoux's Git::CPAN::Patch distribution.

-h

Print a help message and exit. When you specify -h, it ignores all of the other options and arguments.

-i module [ module ... ]

Install the specified modules. With no other switches, this switch is implied.

-I

Load local::lib (think like -I for loading lib paths). Too bad -l was already taken.

-j Config.pm

Load the file that has the CPAN configuration data. This should have the same format as the standard CPAN/Config.pm file, which defines $CPAN::Config as an anonymous hash.

If the file does not exist, cpan dies.

-J

Dump the configuration in the same format that CPAN.pm uses. This is useful for checking the configuration as well as using the dump as a starting point for a new, custom configuration.

-l

List all installed modules with their versions

-L author [ author ... ]

List the modules by the specified authors.

-m

Make the specified modules.

-M mirror1,mirror2,...

A comma-separated list of mirrors to use for just this run. The -P option can find them for you automatically.

-n

Do a dry run, but don't actually install anything. (unimplemented)

-O

Show the out-of-date modules.

-p

Ping the configured mirrors and print a report

-P

Find the best mirrors you could be using and use them for the current session.

-r

Recompiles dynamically loaded modules with CPAN::Shell->recompile.

-s

Drop in the CPAN.pm shell. This command does this automatically if you don't specify any arguments.

-t module [ module ... ]

Run a `make test` on the specified modules.

-T

Do not test modules. Simply install them.

-u

Upgrade all installed modules. Blindly doing this can really break things, so keep a backup.

-v

Print the script version and CPAN.pm version then exit.

-V

Print detailed information about the cpan client.

-w

UNIMPLEMENTED

Turn on cpan warnings. This checks various things, like directory permissions, and tells you about problems you might have.

-x module [ module ... ]

Find close matches to the named modules that you think you might have mistyped. This requires the optional installation of Text::Levenshtein or Text::Levenshtein::Damerau.

-X

Dump all the namespaces to standard output.

Examples

# print a help message
cpan -h

# print the version numbers
cpan -v

# create an autobundle
cpan -a

# recompile modules
cpan -r

# upgrade all installed modules
cpan -u

# install modules ( sole -i is optional )
cpan -i Netscape::Booksmarks Business::ISBN

# force install modules ( must use -i )
cpan -fi CGI::Minimal URI

# install modules but without testing them
cpan -Ti CGI::Minimal URI

Environment variables

There are several components in CPAN.pm that use environment variables. The build tools, ExtUtils::MakeMaker and Module::Build use some, while others matter to the levels above them. Some of these are specified by the Perl Toolchain Gang:

Lancaster Consensus: https://github.com/Perl-Toolchain-Gang/toolchain-site/blob/master/lancaster-consensus.md

Oslo Consensus: https://github.com/Perl-Toolchain-Gang/toolchain-site/blob/master/oslo-consensus.md

NONINTERACTIVE_TESTING

Assume no one is paying attention and skips prompts for distributions that do that correctly. cpan(1) sets this to 1 unless it already has a value (even if that value is false).

PERL_MM_USE_DEFAULT

Use the default answer for a prompted questions. cpan(1) sets this to 1 unless it already has a value (even if that value is false).

CPAN_OPTS

As with PERL5OPT, a string of additional cpan(1) options to add to those you specify on the command line.

CPANSCRIPT_LOGLEVEL

The log level to use, with either the embedded, minimal logger or Log::Log4perl if it is installed. Possible values are the same as the Log::Log4perl levels: TRACE, DEBUG, INFO, WARN, ERROR, and FATAL. The default is INFO.

GIT_COMMAND

The path to the git binary to use for the Git features. The default is /usr/local/bin/git.

Methods

run( ARGS )

Just do it.

The run method returns 0 on success and a positive number on failure. See the section on EXIT CODES for details on the values.

CPAN.pm sends all the good stuff either to STDOUT, or to a temp file if $CPAN::Be_Silent is set. I have to intercept that output so I can find out what happened.

Stolen from File::Path::Expand

EXIT VALUES

The script exits with zero if it thinks that everything worked, or a positive number if it thinks that something failed. Note, however, that in some cases it has to divine a failure by the output of things it does not control. For now, the exit codes are vague:

1	An unknown error

2	The was an external problem

4	There was an internal problem with the script

8	A module failed to install

TO DO

* There is initial support for Log4perl if it is available, but I haven't gone through everything to make the NullLogger work out correctly if Log4perl is not installed.

* When I capture CPAN.pm output, I need to check for errors and report them to the user.

* Warnings switch

* Check then exit

BUGS

* none noted

SEE ALSO

CPAN, App::cpanminus

SOURCE AVAILABILITY

This code is in Github in the CPAN.pm repository:

https://github.com/andk/cpanpm

The source used to be tracked separately in another GitHub repo, but the canonical source is now in the above repo.

CREDITS

Japheth Cleaver added the bits to allow a forced install (-f).

Jim Brandt suggested and provided the initial implementation for the up-to-date and Changes features.

Adam Kennedy pointed out that exit() causes problems on Windows where this script ends up with a .bat extension

David Golden helps integrate this into the CPAN.pm repos.

Jim Keenan fixed up various issues with _download

AUTHOR

brian d foy, <bdfoy@cpan.org>

COPYRIGHT

Copyright (c) 2001-2021, brian d foy, All Rights Reserved.

You may redistribute this under the same terms as Perl itself.