/ 
perl-5.45.1
⭐ Starred 2013 / B::Op_private
Security Advisories (1)
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.

NAME

B::Op_private - OP op_private flag definitions

SYNOPSIS

use B::Op_private;

# flag details for bit 7 of OP_AELEM's op_private:
my $name  = $B::Op_private::bits{aelem}{7}; # OPpLVAL_INTRO
my $value = $B::Op_private::defines{$name}; # 128
my $label = $B::Op_private::labels{$name};  # LVINTRO

# the bit field at bits 5..6 of OP_AELEM's op_private:
my $bf  = $B::Op_private::bits{aelem}{6};
my $mask = $bf->{bitmask}; # etc

DESCRIPTION

This module provides four global hashes:

%B::Op_private::bits
%B::Op_private::defines
%B::Op_private::labels
%B::Op_private::ops_using

which contain information about the per-op meanings of the bits in the op_private field.

%bits

This is indexed by op name and then bit number (0..7). For single bit flags, it returns the name of the define (if any) for that bit:

$B::Op_private::bits{aelem}{7} eq 'OPpLVAL_INTRO';

For bit fields, it returns a hash ref containing details about the field. The same reference will be returned for all bit positions that make up the bit field; so for example these both return the same hash ref:

$bitfield = $B::Op_private::bits{aelem}{5};
$bitfield = $B::Op_private::bits{aelem}{6};

The general format of this hash ref is

{
    # The bit range and mask; these are always present.
    bitmin        => 5,
    bitmax        => 6,
    bitmask       => 0x60,

    # (The remaining keys are optional)

    # The names of any defines that were requested:
    mask_def      => 'OPpFOO_MASK',
    baseshift_def => 'OPpFOO_SHIFT',
    bitcount_def  => 'OPpFOO_BITS',

    # If present, Concise etc will display the value with a 'FOO='
    # prefix. If it equals '-', then Concise will treat the bit
    # field as raw bits and not try to interpret it.
    label         => 'FOO',

    # If present, specifies the names of some defines and the
    # display labels that are used to assign meaning to particu-
    # lar integer values within the bit field; e.g. 3 is dis-
    # played as 'C'.
    enum          => [ qw(
                         1   OPpFOO_A  A
                         2   OPpFOO_B  B
                         3   OPpFOO_C  C
                     )],

};

%defines

This gives the value of every OPp define, e.g.

$B::Op_private::defines{OPpLVAL_INTRO} == 128;

%labels

This gives the short display label for each define, as used by B::Concise and perl -Dx, e.g.

$B::Op_private::labels{OPpLVAL_INTRO} eq 'LVINTRO';

If the label equals '-', then Concise will treat the bit as a raw bit and not try to display it symbolically.

%ops_using

For each define, this gives a reference to an array of op names that use the flag.

@ops_using_lvintro = @{ $B::Op_private::ops_using{OPp_LVAL_INTRO} };