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.
CVSS Score
8.4
EPSS Score
0.002
Published
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.
CVSS Score
9.1
EPSS Score
0.002
Published
2026-07-13
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.
CVSS Score
9.8
EPSS Score
0.004
Published
2026-05-26
A vulnerability was found in Perl. This security issue occurs while Perl for Windows relies on the system path environment variable to find the shell (`cmd.exe`). When running an executable that uses the 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. This flaw allows an attacker with limited privileges to place`cmd.exe` in locations with weak permissions, such as `C:\ProgramData`. By doing so, arbitrary code can be executed when an administrator attempts to use this executable from these compromised locations.
CVSS Score
7.8
EPSS Score
0.004
Published
2024-01-02
CPAN.pm before 2.35 does not verify TLS certificates when downloading distributions over HTTPS.
CVSS Score
8.1
EPSS Score
0.015
Published
2023-04-29
HTTP::Tiny before 0.083, a Perl core module since 5.13.9 and available standalone on CPAN, has an insecure default TLS configuration where users must opt in to verify certificates.
CVSS Score
8.1
EPSS Score
0.017
Published
2023-04-29
Encode.pm, as distributed in Perl through 5.34.0, allows local users to gain privileges via a Trojan horse Encode::ConfigLocal library (in the current working directory) that preempts dynamic module loading. Exploitation requires an unusual configuration, and certain 2021 versions of Encode.pm (3.05 through 3.11). This issue occurs because the || operator evaluates @INC in a scalar context, and thus @INC has only an integer value.
CVSS Score
7.8
EPSS Score
0.014
Published
2021-08-11
regcomp.c in Perl before 5.30.3 allows a buffer overflow via a crafted regular expression because of recursive S_study_chunk calls.
CVSS Score
7.5
EPSS Score
0.06
Published
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.
CVSS Score
8.6
EPSS Score
0.049
Published
2020-06-05
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.
CVSS Score
9.8
EPSS Score
0.117
Published
2018-12-07
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