Use the correct issuer when validating rootCAKeyUpdate

This correctly uses the existing root, and not the same certificate
as the root of the chain to validate.

While we are here, we also turn on self signed certificate signature
checking as this case is actually bringing in trust anchors as
self signed certs, and fix a possible NULL deref.

Fixes CVE-2026-42769

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.foundation>
MergeDate: Mon Jun  8 19:54:01 2026

diff --git a/crypto/cmp/cmp_genm.c b/crypto/cmp/cmp_genm.c
index 905927554fa96414494206fe651ac694553ca2a2..8e974297fde2f78174b2c2f4fc2cc4fb63e03288 100644 (file)
--- a/crypto/cmp/cmp_genm.c
+++ b/crypto/cmp/cmp_genm.c
@@ -223,7 +223,7 @@ static int selfsigned_verify_cb(int ok, X509_STORE_CTX *store_ctx)
         for (i = 0; i < sk_X509_num(trust); i++) {
             issuer = sk_X509_value(trust, i);
             if ((*check_issued)(store_ctx, cert, issuer)) {
-                if (X509_add_cert(chain, cert, X509_ADD_FLAG_UP_REF))
+                if (X509_add_cert(chain, issuer, X509_ADD_FLAG_UP_REF))
                     ok = 1;
                 break;
             }
@@ -256,6 +256,7 @@ static int verify_ss_cert(OSSL_LIB_CTX *libctx, const char *propq,
     if ((csc = X509_STORE_CTX_new_ex(libctx, propq)) == NULL
         || !X509_STORE_CTX_init(csc, ts, target, untrusted))
         goto err;
+    X509_STORE_CTX_set_flags(csc, X509_V_FLAG_CHECK_SS_SIGNATURE);
     X509_STORE_CTX_set_verify_cb(csc, selfsigned_verify_cb);
     ok = X509_verify_cert(csc) > 0;
 
@@ -274,7 +275,8 @@ verify_ss_cert_trans(OSSL_CMP_CTX *ctx, X509 *trusted /* may be NULL */,
     int res = 0;
 
     if (trusted != NULL) {
-        X509_VERIFY_PARAM *vpm = X509_STORE_get0_param(ts);
+        X509_VERIFY_PARAM *vpm = (ts == NULL) ? NULL
+                                              : X509_STORE_get0_param(ts);
 
         if ((ts = X509_STORE_new()) == NULL)
             return 0;