/ 
perl-5.8.2
/ perlnumber
Security Advisories (30)
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-2010-1158 (2010-04-20)

Integer overflow in the regular expression engine in Perl 5.8.x allows context-dependent attackers to cause a denial of service (stack consumption and application crash) by matching a crafted regular expression against a long string.

CVE-2010-4777 (2014-02-10)

The Perl_reg_numbered_buff_fetch function in Perl 5.10.0, 5.12.0, 5.14.0, and other versions, when running with debugging enabled, allows context-dependent attackers to cause a denial of service (assertion failure and application exit) via crafted input that is not properly handled when using certain regular expressions, as demonstrated by causing SpamAssassin and OCSInventory to crash.

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-2018-18314 (2018-12-07)

Perl before 5.26.3 has a buffer overflow via a crafted regular expression that triggers invalid write operations.

CVE-2018-18311 (2018-12-07)

Perl before 5.26.3 and 5.28.x before 5.28.1 has a buffer overflow via a crafted regular expression that triggers invalid write operations.

CVE-2015-8853 (2016-05-25)

The (1) S_reghop3, (2) S_reghop4, and (3) S_reghopmaybe3 functions in regexec.c in Perl before 5.24.0 allow context-dependent attackers to cause a denial of service (infinite loop) via crafted utf-8 data, as demonstrated by "a\x80."

CVE-2013-1667 (2013-03-14)

The rehash mechanism in Perl 5.8.2 through 5.16.x allows context-dependent attackers to cause a denial of service (memory consumption and crash) via a crafted hash key.

CVE-2008-1927 (2008-04-24)

Double free vulnerability in Perl 5.8.8 allows context-dependent attackers to cause a denial of service (memory corruption and crash) via a crafted regular expression containing UTF8 characters. NOTE: this issue might only be present on certain operating systems.

CVE-2003-0900 (2003-12-31)

Perl 5.8.1 on Fedora Core does not properly initialize the random number generator when forking, which makes it easier for attackers to predict random numbers.

CVE-2023-47039 (2023-10-30)

Perl for Windows relies on the system path environment variable to find the shell (cmd.exe). When running an executable which uses Windows Perl interpreter, Perl attempts to find and execute cmd.exe within the operating system. However, due to path search order issues, Perl initially looks for cmd.exe in the current working directory. An attacker with limited privileges can exploit this behavior by placing cmd.exe in locations with weak permissions, such as C:\ProgramData. By doing so, when an administrator attempts to use this executable from these compromised locations, arbitrary code can be executed.

CVE-2023-47100

In Perl before 5.38.2, S_parse_uniprop_string in regcomp.c can write to unallocated space because a property name associated with a \p{...} regular expression construct is mishandled. The earliest affected version is 5.30.0.

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-2012-5195 (2012-12-18)

Heap-based buffer overflow in the Perl_repeatcpy function in util.c in Perl 5.12.x before 5.12.5, 5.14.x before 5.14.3, and 5.15.x before 15.15.5 allows context-dependent attackers to cause a denial of service (memory consumption and crash) or possibly execute arbitrary code via the 'x' string repeat operator.

CVE-2016-2381 (2016-04-08)

Perl might allow context-dependent attackers to bypass the taint protection mechanism in a child process via duplicate environment variables in envp.

CVE-2013-7422 (2015-08-16)

Integer underflow in regcomp.c in Perl before 5.20, as used in Apple OS X before 10.10.5 and other products, allows context-dependent attackers to execute arbitrary code or cause a denial of service (application crash) via a long digit string associated with an invalid backreference within a regular expression.

CVE-2015-8608 (2017-02-07)

The VDir::MapPathA and VDir::MapPathW functions in Perl 5.22 allow remote attackers to cause a denial of service (out-of-bounds read) and possibly execute arbitrary code via a crafted (1) drive letter or (2) pInName argument.

CVE-2020-12723 (2020-06-05)

regcomp.c in Perl before 5.30.3 allows a buffer overflow via a crafted regular expression because of recursive S_study_chunk calls.

CVE-2016-1238 (2016-08-02)

(1) cpan/Archive-Tar/bin/ptar, (2) cpan/Archive-Tar/bin/ptardiff, (3) cpan/Archive-Tar/bin/ptargrep, (4) cpan/CPAN/scripts/cpan, (5) cpan/Digest-SHA/shasum, (6) cpan/Encode/bin/enc2xs, (7) cpan/Encode/bin/encguess, (8) cpan/Encode/bin/piconv, (9) cpan/Encode/bin/ucmlint, (10) cpan/Encode/bin/unidump, (11) cpan/ExtUtils-MakeMaker/bin/instmodsh, (12) cpan/IO-Compress/bin/zipdetails, (13) cpan/JSON-PP/bin/json_pp, (14) cpan/Test-Harness/bin/prove, (15) dist/ExtUtils-ParseXS/lib/ExtUtils/xsubpp, (16) dist/Module-CoreList/corelist, (17) ext/Pod-Html/bin/pod2html, (18) utils/c2ph.PL, (19) utils/h2ph.PL, (20) utils/h2xs.PL, (21) utils/libnetcfg.PL, (22) utils/perlbug.PL, (23) utils/perldoc.PL, (24) utils/perlivp.PL, and (25) utils/splain.PL in Perl 5.x before 5.22.3-RC2 and 5.24 before 5.24.1-RC2 do not properly remove . (period) characters from the end of the includes directory array, which might allow local users to gain privileges via a Trojan horse module under the current working directory.

CVE-2011-2728 (2012-12-21)

The bsd_glob function in the File::Glob module for Perl before 5.14.2 allows context-dependent attackers to cause a denial of service (crash) via a glob expression with the GLOB_ALTDIRFUNC flag, which triggers an uninitialized pointer dereference.

CVE-2020-10878 (2020-06-05)

Perl before 5.30.3 has an integer overflow related to mishandling of a "PL_regkind[OP(n)] == NOTHING" situation. A crafted regular expression could lead to malformed bytecode with a possibility of instruction injection.

CVE-2020-10543 (2020-06-05)

Perl before 5.30.3 on 32-bit platforms allows a heap-based buffer overflow because nested regular expression quantifiers have an integer overflow.

CVE-2018-6913 (2018-04-17)

Heap-based buffer overflow in the pack function in Perl before 5.26.2 allows context-dependent attackers to execute arbitrary code via a large item count.

CVE-2018-18313 (2018-12-07)

Perl before 5.26.3 has a buffer over-read via a crafted regular expression that triggers disclosure of sensitive information from process memory.

CVE-2018-18312 (2018-12-05)

Perl before 5.26.3 and 5.28.0 before 5.28.1 has a buffer overflow via a crafted regular expression that triggers invalid write operations.

CVE-2009-3626 (2009-10-29)

Perl 5.10.1 allows context-dependent attackers to cause a denial of service (application crash) via a UTF-8 character with a large, invalid codepoint, which is not properly handled during a regular-expression match.

CVE-2005-3962 (2005-12-01)

Integer overflow in the format string functionality (Perl_sv_vcatpvfn) in Perl 5.9.2 and 5.8.6 Perl allows attackers to overwrite arbitrary memory and possibly execute arbitrary code via format string specifiers with large values, which causes an integer wrap and leads to a buffer overflow, as demonstrated using format string vulnerabilities in Perl applications.

CVE-2007-5116 (2007-11-07)

Buffer overflow in the polymorphic opcode support in the Regular Expression Engine (regcomp.c) in Perl 5.8 allows context-dependent attackers to execute arbitrary code by switching from byte to Unicode (UTF) characters in a regular expression.

CVE-2011-1487 (2011-04-11)

The (1) lc, (2) lcfirst, (3) uc, and (4) ucfirst functions in Perl 5.10.x, 5.11.x, and 5.12.x through 5.12.3, and 5.13.x through 5.13.11, do not apply the taint attribute to the return value upon processing tainted input, which might allow context-dependent attackers to bypass the taint protection mechanism via a crafted string.

NAME

perlnumber - semantics of numbers and numeric operations in Perl

SYNOPSIS

$n = 1234;		    # decimal integer
$n = 0b1110011;	    # binary integer
$n = 01234;		    # octal integer
$n = 0x1234;	    # hexadecimal integer
$n = 12.34e-56;	    # exponential notation
$n = "-12.34e56";	    # number specified as a string
$n = "1234";	    # number specified as a string

DESCRIPTION

This document describes how Perl internally handles numeric values.

Perl's operator overloading facility is completely ignored here. Operator overloading allows user-defined behaviors for numbers, such as operations over arbitrarily large integers, floating points numbers with arbitrary precision, operations over "exotic" numbers such as modular arithmetic or p-adic arithmetic, and so on. See overload for details.

Storing numbers

Perl can internally represent numbers in 3 different ways: as native integers, as native floating point numbers, and as decimal strings. Decimal strings may have an exponential notation part, as in "12.34e-56". Native here means "a format supported by the C compiler which was used to build perl".

The term "native" does not mean quite as much when we talk about native integers, as it does when native floating point numbers are involved. The only implication of the term "native" on integers is that the limits for the maximal and the minimal supported true integral quantities are close to powers of 2. However, "native" floats have a most fundamental restriction: they may represent only those numbers which have a relatively "short" representation when converted to a binary fraction. For example, 0.9 cannot be represented by a native float, since the binary fraction for 0.9 is infinite:

binary0.1110011001100...

with the sequence 1100 repeating again and again. In addition to this limitation, the exponent of the binary number is also restricted when it is represented as a floating point number. On typical hardware, floating point values can store numbers with up to 53 binary digits, and with binary exponents between -1024 and 1024. In decimal representation this is close to 16 decimal digits and decimal exponents in the range of -304..304. The upshot of all this is that Perl cannot store a number like 12345678901234567 as a floating point number on such architectures without loss of information.

Similarly, decimal strings can represent only those numbers which have a finite decimal expansion. Being strings, and thus of arbitrary length, there is no practical limit for the exponent or number of decimal digits for these numbers. (But realize that what we are discussing the rules for just the storage of these numbers. The fact that you can store such "large" numbers does not mean that the operations over these numbers will use all of the significant digits. See "Numeric operators and numeric conversions" for details.)

In fact numbers stored in the native integer format may be stored either in the signed native form, or in the unsigned native form. Thus the limits for Perl numbers stored as native integers would typically be -2**31..2**32-1, with appropriate modifications in the case of 64-bit integers. Again, this does not mean that Perl can do operations only over integers in this range: it is possible to store many more integers in floating point format.

Summing up, Perl numeric values can store only those numbers which have a finite decimal expansion or a "short" binary expansion.

Numeric operators and numeric conversions

As mentioned earlier, Perl can store a number in any one of three formats, but most operators typically understand only one of those formats. When a numeric value is passed as an argument to such an operator, it will be converted to the format understood by the operator.

Six such conversions are possible:

native integer        --> native floating point	(*)
native integer        --> decimal string
native floating_point --> native integer		(*)
native floating_point --> decimal string		(*)
decimal string        --> native integer
decimal string        --> native floating point	(*)

These conversions are governed by the following general rules:

  • If the source number can be represented in the target form, that representation is used.

  • If the source number is outside of the limits representable in the target form, a representation of the closest limit is used. (Loss of information)

  • If the source number is between two numbers representable in the target form, a representation of one of these numbers is used. (Loss of information)

  • In native floating point --> native integer conversions the magnitude of the result is less than or equal to the magnitude of the source. ("Rounding to zero".)

  • If the decimal string --> native integer conversion cannot be done without loss of information, the result is compatible with the conversion sequence decimal_string --> native_floating_point --> native_integer. In particular, rounding is strongly biased to 0, though a number like "0.99999999999999999999" has a chance of being rounded to 1.

RESTRICTION: The conversions marked with (*) above involve steps performed by the C compiler. In particular, bugs/features of the compiler used may lead to breakage of some of the above rules.

Flavors of Perl numeric operations

Perl operations which take a numeric argument treat that argument in one of four different ways: they may force it to one of the integer/floating/ string formats, or they may behave differently depending on the format of the operand. Forcing a numeric value to a particular format does not change the number stored in the value.

All the operators which need an argument in the integer format treat the argument as in modular arithmetic, e.g., mod 2**32 on a 32-bit architecture. sprintf "%u", -1 therefore provides the same result as sprintf "%u", ~0.

Arithmetic operators

The binary operators + - * / % == != > < >= <= and the unary operators - abs and -- will attempt to convert arguments to integers. If both conversions are possible without loss of precision, and the operation can be performed without loss of precision then the integer result is used. Otherwise arguments are converted to floating point format and the floating point result is used. The caching of conversions (as described above) means that the integer conversion does not throw away fractional parts on floating point numbers.

++

++ behaves as the other operators above, except that if it is a string matching the format /^[a-zA-Z]*[0-9]*\z/ the string increment described in perlop is used.

Arithmetic operators during use integer

In scopes where use integer; is in force, nearly all the operators listed above will force their argument(s) into integer format, and return an integer result. The exceptions, abs, ++ and --, do not change their behavior with use integer;

Other mathematical operators

Operators such as **, sin and exp force arguments to floating point format.

Bitwise operators

Arguments are forced into the integer format if not strings.

Bitwise operators during use integer

forces arguments to integer format. Also shift operations internally use signed integers rather than the default unsigned.

Operators which expect an integer

force the argument into the integer format. This is applicable to the third and fourth arguments of sysread, for example.

Operators which expect a string

force the argument into the string format. For example, this is applicable to printf "%s", $value.

Though forcing an argument into a particular form does not change the stored number, Perl remembers the result of such conversions. In particular, though the first such conversion may be time-consuming, repeated operations will not need to redo the conversion.

AUTHOR

Ilya Zakharevich ilya@math.ohio-state.edu

Editorial adjustments by Gurusamy Sarathy <gsar@ActiveState.com>

Updates for 5.8.0 by Nicholas Clark <nick@ccl4.org>

SEE ALSO

overload, perlop