Fix CVE-2026-41989: Denial of Service and buffer overflow via crafted ECDH ciphertext

Resolves: RHEL-182718

libgcrypt-1.11.0-montgomery-zeroes.patch

@@ -0,0 +1,40 @@
+From 5ba63ec41a6e734c9ff82e20e4f84ac94c59ae27 Mon Sep 17 00:00:00 2001
+From: NIIBE Yutaka <gniibe@fsij.org>
+Date: Fri, 10 Apr 2026 16:58:57 +0900
+Subject: [PATCH] cipher:ecc: Fix decoding a point on Montgomery curve.
+
+* cipher/ecc-misc.c (_gcry_ecc_mont_decodepoint): Fix the padding
+mistake and add updating RAWMPILEN.
+
+--
+
+Reported by Calif.io in collaboration with Claude and Anthropic
+Research.
+
+GnuPG-bug-id: 8211
+Fixes-commit: bbe15758c893dbf546416c1a6bccdad1ab000ad7
+Suggested-by: Bronson Yen <bronson@calif.io>
+Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
+---
+ cipher/ecc-misc.c | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/cipher/ecc-misc.c b/cipher/ecc-misc.c
+index 0c387c27..be4e2862 100644
+--- a/cipher/ecc-misc.c
++++ b/cipher/ecc-misc.c
+@@ -324,7 +324,10 @@ _gcry_ecc_mont_decodepoint (gcry_mpi_t pk, mpi_ec_t ctx, mpi_point_t result)
+         *--p = *buf++;
+ 
+       if (rawmpilen < nbytes)
+-        memset (rawmpi + nbytes - rawmpilen, 0, nbytes - rawmpilen);
++        {
++          memset (rawmpi + rawmpilen, 0, nbytes - rawmpilen);
++          rawmpilen = nbytes;
++        }
+     }
+   else
+     {
+-- 
+2.54.0
+

libgcrypt.spec

@@ -88,6 +88,8 @@ Patch22: libgcrypt-1.10.0-marvin.patch
 Patch23: libgcrypt-1.10.0-marvin2.patch
 # https://gitlab.com/redhat-crypto/libgcrypt/libgcrypt-mirror/-/merge_requests/19/
 Patch24: libgcrypt-1.10.0-marvin3.patch
+# https://dev.gnupg.org/T8211.html
+Patch25: libgcrypt-1.11.0-montgomery-zeroes.patch
 
 %global gcrylibdir %{_libdir}
 %global gcrysoname libgcrypt.so.20
@@ -145,6 +147,7 @@ applications using libgcrypt.
 %patch22 -p1
 %patch23 -p1
 %patch24 -p1
+%patch25 -p1
 
 %build
 # This package has a configure test which uses ASMs, but does not link the