/ 
perl-5.37.10
⭐ Starred 2013 / perlcheat
Security Advisories (4)
CVE-2024-56406 (2025-04-13)

A heap buffer overflow vulnerability was discovered in Perl. Release branches 5.34, 5.36, 5.38 and 5.40 are affected, including development versions from 5.33.1 through 5.41.10. When there are non-ASCII bytes in the left-hand-side of the `tr` operator, `S_do_trans_invmap` can overflow the destination pointer `d`.    $ perl -e '$_ = "\x{FF}" x 1000000; tr/\xFF/\x{100}/;'    Segmentation fault (core dumped) It is believed that this vulnerability can enable Denial of Service and possibly Code Execution attacks on platforms that lack sufficient defenses.

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-2026-8376 (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-2025-40909 (2025-05-30)

Perl threads have a working directory race condition where file operations may target unintended paths. If a directory handle is open at thread creation, the process-wide current working directory is temporarily changed in order to clone that handle for the new thread, which is visible from any third (or more) thread already running. This may lead to unintended operations such as loading code or accessing files from unexpected locations, which a local attacker may be able to exploit. The bug was introduced in commit 11a11ecf4bea72b17d250cfb43c897be1341861e and released in Perl version 5.13.6

NAME

perlcheat - Perl 5 Cheat Sheet

DESCRIPTION

This 'cheat sheet' is a handy reference, meant for beginning Perl programmers. Not everything is mentioned, but 195 features may already be overwhelming.

The sheet

CONTEXTS  SIGILS  ref        ARRAYS        HASHES
void      $scalar SCALAR     @array        %hash
scalar    @array  ARRAY      @array[0, 2]  @hash{'a', 'b'}
list      %hash   HASH       $array[0]     $hash{'a'}
          &sub    CODE
          *glob   GLOB       SCALAR VALUES
                  FORMAT     number, string, ref, glob, undef
REFERENCES
\      reference       $$foo[1]       aka $foo->[1]
$@%&*  dereference     $$foo{bar}     aka $foo->{bar}
[]     anon. arrayref  ${$$foo[1]}[2] aka $foo->[1]->[2]
{}     anon. hashref   ${$$foo[1]}[2] aka $foo->[1][2]
\()    list of refs
                       SYNTAX
OPERATOR PRECEDENCE    foreach (LIST) { }     for (a;b;c) { }
->                     while   (e) { }        until (e)   { }
++ --                  if      (e) { } elsif (e) { } else { }
**                     unless  (e) { } elsif (e) { } else { }
! ~ \ u+ u-            given   (e) { when (e) {} default {} }
=~ !~
* / % x                 NUMBERS vs STRINGS  FALSE vs TRUE
+ - .                   =          =        undef, "", 0, "0"
<< >>                   +          .        anything else
named uops              == !=      eq ne
< > <= >= lt gt le ge   < > <= >=  lt gt le ge
== != <=> eq ne cmp ~~  <=>        cmp
&
| ^             REGEX MODIFIERS       REGEX METACHARS
&&              /i case insensitive   ^      string begin
|| //           /m line based ^$      $      str end (bfr \n)
.. ...          /s . includes \n      +      one or more
?:              /x /xx ign. wh.space  *      zero or more
= += last goto  /p preserve           ?      zero or one
, =>            /a ASCII    /aa safe  {3,7}  repeat in range
list ops        /l locale   /d  dual  |      alternation
not             /u Unicode            []     character class
and             /e evaluate /ee rpts  \b     boundary
or xor          /g global             \z     string end
                /o compile pat once   ()     capture
DEBUG                                 (?:p)  no capture
-MO=Deparse     REGEX CHARCLASSES     (?#t)  comment
-MO=Terse       .   [^\n]             (?=p)  ZW pos ahead
-D##            \s  whitespace        (?!p)  ZW neg ahead
-d:Trace        \w  word chars        (?<=p) ZW pos behind \K
                \d  digits            (?<!p) ZW neg behind
CONFIGURATION   \pP named property    (?>p)  no backtrack
perl -V:ivsize  \h  horiz.wh.space    (?|p|p)branch reset
                \R  linebreak         (?<n>p)named capture
                \S \W \D \H negate    \g{n}  ref to named cap
                                      \K     keep left part
FUNCTION RETURN LISTS
stat      localtime    caller         SPECIAL VARIABLES
 0 dev    0 second      0 package     $_    default variable
 1 ino    1 minute      1 filename    $0    program name
 2 mode   2 hour        2 line        $/    input separator
 3 nlink  3 day         3 subroutine  $\    output separator
 4 uid    4 month-1     4 hasargs     $|    autoflush
 5 gid    5 year-1900   5 wantarray   $!    sys/libcall error
 6 rdev   6 weekday     6 evaltext    $@    eval error
 7 size   7 yearday     7 is_require  $$    process ID
 8 atime  8 is_dst      8 hints       $.    line number
 9 mtime                9 bitmask     @ARGV command line args
10 ctime               10 hinthash    @INC  include paths
11 blksz               3..10 only     @_    subroutine args
12 blcks               with EXPR      %ENV  environment

ACKNOWLEDGEMENTS

The first version of this document appeared on Perl Monks, where several people had useful suggestions. Thank you, Perl Monks.

A special thanks to Damian Conway, who didn't only suggest important changes, but also took the time to count the number of listed features and make a Raku version to show that Perl will stay Perl.

AUTHOR

Juerd Waalboer <#####@juerd.nl>, with the help of many Perl Monks.

SEE ALSO