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perl-5.42.0
⭐ Starred 2013 / Fatal
Security Advisories (5)
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.

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-2026-13221 (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-2026-4176 (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.

NAME

Fatal - Replace functions with equivalents which succeed or die

SYNOPSIS

use Fatal qw(open close);

open(my $fh, "<", $filename);  # No need to check errors!

use File::Copy qw(move);
use Fatal qw(move);

move($file1, $file2); # No need to check errors!

sub juggle { . . . }
Fatal->import('juggle');

BEST PRACTICE

Fatal has been obsoleted by the new autodie pragma. Please use autodie in preference to Fatal. autodie supports lexical scoping, throws real exception objects, and provides much nicer error messages.

The use of :void with Fatal is discouraged.

DESCRIPTION

Fatal provides a way to conveniently replace functions which normally return a false value when they fail with equivalents which raise exceptions if they are not successful. This lets you use these functions without having to test their return values explicitly on each call. Exceptions can be caught using eval{}. See perlfunc and perlvar for details.

The do-or-die equivalents are set up simply by calling Fatal's import routine, passing it the names of the functions to be replaced. You may wrap both user-defined functions and overridable CORE operators (except exec, system, print, or any other built-in that cannot be expressed via prototypes) in this way.

If the symbol :void appears in the import list, then functions named later in that import list raise an exception only when these are called in void context--that is, when their return values are ignored. For example

use Fatal qw/:void open close/;

# properly checked, so no exception raised on error
if (not open(my $fh, '<', '/bogotic') {
    warn "Can't open /bogotic: $!";
}

# not checked, so error raises an exception
close FH;

The use of :void is discouraged, as it can result in exceptions not being thrown if you accidentally call a method without void context. Use autodie instead if you need to be able to disable autodying/Fatal behaviour for a small block of code.

DIAGNOSTICS

Bad subroutine name for Fatal: %s

You've called Fatal with an argument that doesn't look like a subroutine name, nor a switch that this version of Fatal understands.

%s is not a Perl subroutine

You've asked Fatal to try and replace a subroutine which does not exist, or has not yet been defined.

%s is neither a builtin, nor a Perl subroutine

You've asked Fatal to replace a subroutine, but it's not a Perl built-in, and Fatal couldn't find it as a regular subroutine. It either doesn't exist or has not yet been defined.

Cannot make the non-overridable %s fatal

You've tried to use Fatal on a Perl built-in that can't be overridden, such as print or system, which means that Fatal can't help you, although some other modules might. See the "SEE ALSO" section of this documentation.

Internal error: %s

You've found a bug in Fatal. Please report it using the perlbug command.

BUGS

Fatal clobbers the context in which a function is called and always makes it a scalar context, except when the :void tag is used. This problem does not exist in autodie.

"Used only once" warnings can be generated when autodie or Fatal is used with package filehandles (eg, FILE). It's strongly recommended you use scalar filehandles instead.

AUTHOR

Original module by Lionel Cons (CERN).

Prototype updates by Ilya Zakharevich <ilya@math.ohio-state.edu>.

autodie support, bugfixes, extended diagnostics, system support, and major overhauling by Paul Fenwick <pjf@perltraining.com.au>

LICENSE

This module is free software, you may distribute it under the same terms as Perl itself.

SEE ALSO

autodie for a nicer way to use lexical Fatal.

IPC::System::Simple for a similar idea for calls to system() and backticks.