Avoid NULL dereference in password-based CMS decryption

The keyDerivationAlgorithm field is OPTIONAL in the ASN.1 but required
for password-based CMS. Check that the field is present before using it
to avoid a crash.

From Igor Ustinov via OpenSSL

1 files changed, 5 insertions, 1 deletions

diff --git a/src/lib/libcrypto/cms/cms_pwri.c b/src/lib/libcrypto/cms/cms_pwri.c
index f64f4ab68c..d282d1d42f 100644
--- a/src/lib/libcrypto/cms/cms_pwri.c
+++ b/src/lib/libcrypto/cms/cms_pwri.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: cms_pwri.c,v 1.35 2025/09/30 12:51:16 tb Exp $ */
+/* $OpenBSD: cms_pwri.c,v 1.36 2026/06/09 12:12:34 tb Exp $ */
 /*
  * Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project.
@@ -386,6 +386,10 @@ cms_RecipientInfo_pwri_crypt(CMS_ContentInfo *cms, CMS_RecipientInfo *ri,
         }
 
         algtmp = pwri->keyDerivationAlgorithm;
+        if (algtmp == NULL) {
+                CMSerror(CMS_R_INVALID_KEY_ENCRYPTION_PARAMETER);
+                goto err;
+        }
 
         /* Finish password based key derivation to setup key in "ctx" */