[wrynose][PATCH 1/2] perl: fix CVE-2026-13221

[Jaipaul Cheernam <jaipaul.cheernam@est.tech>]

This patch applies the upstream fix as referenced in [1], using the
commit shown in [2].

[1] https://nvd.nist.gov/vuln/detail/CVE-2026-13221
[2] https://github.com/Perl/perl5/commit/03f74bbbd3a68350d926ee93d56ee4808c28c4c7

Signed-off-by: Jaipaul Cheernam <jaipaul.cheernam@est.tech>
---
 .../perl/files/CVE-2026-13221.patch           | 75 +++++++++++++++++++
 meta/recipes-devtools/perl/perl_5.42.0.bb     |  1 +
 2 files changed, 76 insertions(+)
 create mode 100644 meta/recipes-devtools/perl/files/CVE-2026-13221.patch

diff --git a/meta/recipes-devtools/perl/files/CVE-2026-13221.patch b/meta/recipes-devtools/perl/files/CVE-2026-13221.patch
new file mode 100644
index 0000000000..03396f3e43
--- /dev/null
+++ b/meta/recipes-devtools/perl/files/CVE-2026-13221.patch
@@ -0,0 +1,75 @@
+From 03f74bbbd3a68350d926ee93d56ee4808c28c4c7 Mon Sep 17 00:00:00 2001
+From: Karl Williamson <khw@cpan.org>
+Date: Thu, 26 Mar 2026 10:13:49 -0600
+Subject: [PATCH] regcomp_study: Don't create a trie that would overflow
+
+This addresses GH #23388
+
+The design of the trie compiling code is to batch extra long tries into
+smaller chunks that fit into whatever limitations there are.  However,
+this ticket shows that that isn't always being done.
+
+In this case, a bunch of branches that have TAIL operands can be
+combined together, and the final TAIL is used.  And the code requires
+that the delta between the first branch and this final TAIL fit into a
+16-bit field.  That is the root cause of this bug.
+
+I'm not familiar enough with the trie construction code to easily
+understand why the final tail needs to be used here.  So this patch
+simply doesn't optimize a sequence of branches into a trie that would
+overflow.
+
+This could be revisited by someone who knows more about this than I, or
+earlier in the development cycle.
+
+CVE: CVE-2026-13221
+Upstream-Status: Backport [https://github.com/Perl/perl5/commit/03f74bbbd3a68350d926ee93d56ee4808c28c4c7]
+Signed-off-by: Jaipaul Cheernam <jaipaul.cheernam@est.tech>
+---
+ regcomp_study.c     | 10 ++++++++++
+ t/re/pat_advanced.t |  9 +++++++++
+ 2 files changed, 19 insertions(+)
+
+diff --git a/regcomp_study.c b/regcomp_study.c
+index db7ab3a409..a1b2c3d4e5 100644
+--- a/regcomp_study.c
++++ b/regcomp_study.c
+@@ -1933,6 +1933,16 @@ Perl_study_chunk(pTHX_
+                             tail = regnext( tail );
+                         }
+ 
++                        /* The code below currently saves the difference from
++                         * start to finish in a 16-bit field, causing
++                         * GH #23388.  This defeats the design of batching
++                         * tries into chunks that each fit.  khw thinks it is
++                         * too late in the 5.44 cycle to relook at the design,
++                         * so for now anyway, don't make a trie that would
++                         * overflow */
++                        if (tail - startbranch >= U16_MAX) {
++                            continue;
++                        }
+ 
+                         DEBUG_TRIE_COMPILE_r({
+                             regprop(RExC_rx, RExC_mysv, tail, NULL, pRExC_state);
+diff --git a/t/re/pat_advanced.t b/t/re/pat_advanced.t
+index 398680838d..c9e389ecb3 100644
+--- a/t/re/pat_advanced.t
++++ b/t/re/pat_advanced.t
+@@ -4898,6 +4898,15 @@ EOF_DEBUG_OUT
+         $x =~ s/^[\x{0301}\x{030C}]+//;
+     }
+ 
++    { # GH #23388
++        fresh_perl_is(<<~'PROG', , "", {}, "Avoid trie overflow");
++            my $x = join "|", "aaa".."mzz";
++            my $y = join "|", "naa".."zzz";
++            use re 'Debug';
++            "fnord" =~ m/(?:$x)|(?:$y)/;
++            PROG
++    }
++
+ 
+     # !!! NOTE that tests that aren't at all likely to crash perl should go
+     # a ways above, above these last ones.  There's a comment there that, like
+-- 
+2.43.0
diff --git a/meta/recipes-devtools/perl/perl_5.42.0.bb b/meta/recipes-devtools/perl/perl_5.42.0.bb
index 1833b7a352..1a3451b747 100644
--- a/meta/recipes-devtools/perl/perl_5.42.0.bb
+++ b/meta/recipes-devtools/perl/perl_5.42.0.bb
@@ -18,6 +18,7 @@ SRC_URI = "https://www.cpan.org/src/5.0/perl-${PV}.tar.gz;name=perl \
            file://0001-cpan-Sys-Syslog-Makefile.PL-Fix-_PATH_LOG-for-determ.patch \
            file://CVE-2026-8376-01.patch \
            file://CVE-2026-8376-02.patch \
+           file://CVE-2026-13221.patch \
            "
 SRC_URI:append:class-native = " \
            file://perl-configpm-switch.patch \