/ 
perl-5.9.0
/ Encode::Unicode
Security Advisories (26)
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-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-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-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-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-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-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-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-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-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-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-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-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-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-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-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-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-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-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-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.

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.

NAME

Encode::Unicode -- Various Unicode Transformation Formats

SYNOPSIS

use Encode qw/encode decode/; 
$ucs2 = encode("UCS-2BE", $utf8);
$utf8 = decode("UCS-2BE", $ucs2);

ABSTRACT

This module implements all Character Encoding Schemes of Unicode that are officially documented by Unicode Consortium (except, of course, for UTF-8, which is a native format in perl).

http://www.unicode.org/glossary/ says:

Character Encoding Scheme A character encoding form plus byte serialization. There are Seven character encoding schemes in Unicode: UTF-8, UTF-16, UTF-16BE, UTF-16LE, UTF-32 (UCS-4), UTF-32BE (UCS-4BE) and UTF-32LE (UCS-4LE), and UTF-7.

Since UTF-7 is a 7-bit (re)encoded version of UTF-16BE, It is not part of Unicode's Character Encoding Scheme. It is separately implemented in Encode::Unicode::UTF7. For details see Encode::Unicode::UTF7.

Quick Reference
              Decodes from ord(N)           Encodes chr(N) to...
     octet/char BOM S.P d800-dfff  ord > 0xffff     \x{1abcd} ==
---------------+-----------------+------------------------------
UCS-2BE	2   N   N  is bogus                  Not Available
UCS-2LE       2   N   N     bogus                  Not Available
UTF-16      2/4   Y   Y  is   S.P           S.P            BE/LE
UTF-16BE    2/4   N   Y       S.P           S.P    0xd82a,0xdfcd
UTF-16LE	2   N   Y       S.P           S.P    0x2ad8,0xcddf
UTF-32	4   Y   -  is bogus         As is            BE/LE
UTF-32BE	4   N   -     bogus         As is       0x0001abcd
UTF-32LE	4   N   -     bogus         As is       0xcdab0100
UTF-8       1-4   -   -     bogus   >= 4 octets   \xf0\x9a\af\8d
---------------+-----------------+------------------------------

Size, Endianness, and BOM

You can categorize these CES by 3 criteria: size of each character, endianness, and Byte Order Mark.

by size

UCS-2 is a fixed-length encoding with each character taking 16 bits. It does not support surrogate pairs. When a surrogate pair is encountered during decode(), its place is filled with \x{FFFD} if CHECK is 0, or the routine croaks if CHECK is 1. When a character whose ord value is larger than 0xFFFF is encountered, its place is filled with \x{FFFD} if CHECK is 0, or the routine croaks if CHECK is 1.

UTF-16 is almost the same as UCS-2 but it supports surrogate pairs. When it encounters a high surrogate (0xD800-0xDBFF), it fetches the following low surrogate (0xDC00-0xDFFF) and desurrogates them to form a character. Bogus surrogates result in death. When \x{10000} or above is encountered during encode(), it ensurrogates them and pushes the surrogate pair to the output stream.

UTF-32 (UCS-4) is a fixed-length encoding with each character taking 32 bits. Since it is 32-bit, there is no need for surrogate pairs.

by endianness

The first (and now failed) goal of Unicode was to map all character repertoires into a fixed-length integer so that programmers are happy. Since each character is either a short or long in C, you have to pay attention to the endianness of each platform when you pass data to one another.

Anything marked as BE is Big Endian (or network byte order) and LE is Little Endian (aka VAX byte order). For anything not marked either BE or LE, a character called Byte Order Mark (BOM) indicating the endianness is prepended to the string.

BOM as integer when fetched in network byte order
            16         32 bits/char
-------------------------
BE      0xFeFF 0x0000FeFF
LE      0xFFeF 0xFFFe0000
-------------------------

This modules handles the BOM as follows.

  • When BE or LE is explicitly stated as the name of encoding, BOM is simply treated as a normal character (ZERO WIDTH NO-BREAK SPACE).

  • When BE or LE is omitted during decode(), it checks if BOM is at the beginning of the string; if one is found, the endianness is set to what the BOM says. If no BOM is found, the routine dies.

  • When BE or LE is omitted during encode(), it returns a BE-encoded string with BOM prepended. So when you want to encode a whole text file, make sure you encode() the whole text at once, not line by line or each line, not file, will have a BOM prepended.

  • UCS-2 is an exception. Unlike others, this is an alias of UCS-2BE. UCS-2 is already registered by IANA and others that way.

Surrogate Pairs

To say the least, surrogate pairs were the biggest mistake of the Unicode Consortium. But according to the late Douglas Adams in The Hitchhiker's Guide to the Galaxy Trilogy, In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move. Their mistake was not of this magnitude so let's forgive them.

(I don't dare make any comparison with Unicode Consortium and the Vogons here ;) Or, comparing Encode to Babel Fish is completely appropriate -- if you can only stick this into your ear :)

Surrogate pairs were born when the Unicode Consortium finally admitted that 16 bits were not big enough to hold all the world's character repertoires. But they already made UCS-2 16-bit. What do we do?

Back then, the range 0xD800-0xDFFF was not allocated. Let's split that range in half and use the first half to represent the upper half of a character and the second half to represent the lower half of a character. That way, you can represent 1024 * 1024 = 1048576 more characters. Now we can store character ranges up to \x{10ffff} even with 16-bit encodings. This pair of half-character is now called a surrogate pair and UTF-16 is the name of the encoding that embraces them.

Here is a formula to ensurrogate a Unicode character \x{10000} and above;

$hi = ($uni - 0x10000) / 0x400 + 0xD800;
$lo = ($uni - 0x10000) % 0x400 + 0xDC00;

And to desurrogate;

$uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00);

Note this move has made \x{D800}-\x{DFFF} into a forbidden zone but perl does not prohibit the use of characters within this range. To perl, every one of \x{0000_0000} up to \x{ffff_ffff} (*) is a character.

(*) or \x{ffff_ffff_ffff_ffff} if your perl is compiled with 64-bit
integer support!

SEE ALSO

Encode, Encode::Unicode::UTF7, http://www.unicode.org/glossary/, http://www.unicode.org/unicode/faq/utf_bom.html,

RFC 2781 http://rfc.net/rfc2781.html,

The whole Unicode standard http://www.unicode.org/unicode/uni2book/u2.html

Ch. 15, pp. 403 of Programming Perl (3rd Edition) by Larry Wall, Tom Christiansen, Jon Orwant; O'Reilly & Associates; ISBN 0-596-00027-8