From b50ffea546e762943dee8c68e6707dba02d29cbe Mon Sep 17 00:00:00 2001
From: Karel Miko <karel.miko@gmail.com>
Date: Sat, 1 Aug 2026 15:43:21 +0200
Subject: [PATCH] PBES - fix stack over-read with malformed PBES2 parameters

---
 src/misc/pbes/pbes.c                   |  2 ++
 src/misc/pbes/pbes2.c                  |  3 +++
 tests/pem/pkcs/invalid/pbes2-no-iv.pk8 | 12 ++++++++++++
 3 files changed, 17 insertions(+)
 create mode 100644 tests/pem/pkcs/invalid/pbes2-no-iv.pk8

diff --git a/src/misc/pbes/pbes.c b/src/misc/pbes/pbes.c
index b4231234a..22e711589 100644
--- a/src/misc/pbes/pbes.c
+++ b/src/misc/pbes/pbes.c
@@ -44,6 +44,8 @@ int pbes_decrypt(const pbes_arg  *arg, unsigned char *dec_data, unsigned long *d
    if (arg->iv != NULL) {
       iv = arg->iv->data;
    } else {
+      /* PBES1 derives key and IV in one go, the IV follows the key in k; blocklen is 0 for PBES2, which has no IV to derive from */
+      if (arg->type.blocklen != (unsigned long)cipher_descriptor[cid].block_length) return CRYPT_INVALID_PACKET;
       iv = k + klen;
       klen += arg->type.blocklen;
    }
diff --git a/src/misc/pbes/pbes2.c b/src/misc/pbes/pbes2.c
index a8db5bd46..1b6ebf812 100644
--- a/src/misc/pbes/pbes2.c
+++ b/src/misc/pbes/pbes2.c
@@ -197,6 +197,9 @@ int pbes2_extract(const ltc_asn1_list *s, pbes_arg *res)
       } else {
          return CRYPT_INVALID_PACKET;
       }
+   } else {
+      /* PBES2 always carries the IV in the parameters, there is nothing to derive it from */
+      return CRYPT_INVALID_PACKET;
    }
 
    return CRYPT_OK;
diff --git a/tests/pem/pkcs/invalid/pbes2-no-iv.pk8 b/tests/pem/pkcs/invalid/pbes2-no-iv.pk8
new file mode 100644
index 000000000..861c5242a
--- /dev/null
+++ b/tests/pem/pkcs/invalid/pbes2-no-iv.pk8
@@ -0,0 +1,12 @@
+-----BEGIN ENCRYPTED PRIVATE KEY-----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+-----END ENCRYPTED PRIVATE KEY-----