[31670] in CVS-changelog-for-Kerberos-V5
krb5 commit [krb5-1.22]: Prevent null dereference in PKINIT CMS
daemon@ATHENA.MIT.EDU (ghudson@mit.edu)
Mon Nov 9 12:01:52 2026
From: ghudson@mit.edu
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Date: Mon, 9 Nov 2026 12:00:36 -0500 (EST)
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https://github.com/krb5/krb5/commit/1b3a8db6567ff840b3cda173c9f0a9802b5fef8e
commit 1b3a8db6567ff840b3cda173c9f0a9802b5fef8e
Author: Greg Hudson <ghudson@mit.edu>
Date: Sun Aug 2 21:44:11 2026 -0400
Prevent null dereference in PKINIT CMS processing
In cms_signeddata_verify(), where we use CMS_get0_content(), check
that the dereferenced result is non-null as well as the result itself.
(The result itself is a pointer to the eContent slot, whether or not
the decoded ASN.1 value contained an eContent field, and will only be
null if the CMS_ContentInfo object has an unexpected type.)
CVE-2026-71200:
If a KDC is configured to allow PKINIT authentication, an
unauthenticated attacker can trigger a null pointer dereference,
causing the process to terminate. Discovered by Claude and Ada
Logics, and independently by Erin Liman using DeepSeek.
(cherry picked from commit 6a5d772002c1764bd14934ccb6684f0cce15d617)
ticket: 9227
version_fixed: 1.22.3
src/plugins/preauth/pkinit/pkinit_crypto_openssl.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c b/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c
index 7d0545419..2fbda32de 100644
--- a/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c
+++ b/src/plugins/preauth/pkinit/pkinit_crypto_openssl.c
@@ -2030,7 +2030,8 @@ cms_signeddata_verify(krb5_context context,
unsigned char *d;
*is_signed = 0;
octets = CMS_get0_content(cms);
- if (!octets || (ASN1_STRING_type(*octets) != V_ASN1_OCTET_STRING)) {
+ if (octets == NULL || *octets == NULL ||
+ (ASN1_STRING_type(*octets) != V_ASN1_OCTET_STRING)) {
retval = KRB5KDC_ERR_PREAUTH_FAILED;
krb5_set_error_message(context, retval,
_("Invalid pkinit packet: octet string "
@@ -2085,9 +2086,10 @@ cms_signeddata_verify(krb5_context context,
*is_signed = 0;
/* We cannot use CMS_dataInit because there may be no digest */
octets = CMS_get0_content(cms);
- if (octets)
+ if (octets != NULL && *octets != NULL) {
out = BIO_new_mem_buf(ASN1_STRING_get0_data(*octets),
ASN1_STRING_length(*octets));
+ }
if (out == NULL)
goto cleanup;
} else {
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