diff --git a/include/Domito.h b/include/Domito.h
index 3a1f9b4..68d22f4 100644
--- a/include/Domito.h
+++ b/include/Domito.h
@@ -178,6 +178,7 @@ EXTERN_C
 UINT32
 DomitoGetPortableExecutableDigestKind(
     _In_ PUCHAR pPeBytes,
+    _In_ ULONG PeSize,
     _In_ PIMAGE_DATA_DIRECTORY pImgDataDirectory
 );
 
diff --git a/src/Domito.CodeIntegrity.cpp b/src/Domito.CodeIntegrity.cpp
index d181ae7..8a22b33 100644
--- a/src/Domito.CodeIntegrity.cpp
+++ b/src/Domito.CodeIntegrity.cpp
@@ -20,16 +20,25 @@ _IRQL_requires_max_(DISPATCH_LEVEL)
 UINT32
 DomitoGetPortableExecutableDigestKind(
     _In_ PUCHAR pPeBytes,
+    _In_ ULONG PeSize,
     _In_ PIMAGE_DATA_DIRECTORY pImgDataDirectory
 )
 {
-    if (!pImgDataDirectory[IMAGE_DIRECTORY_ENTRY_SECURITY].VirtualAddress)
+    const ULONG securityRva = pImgDataDirectory[IMAGE_DIRECTORY_ENTRY_SECURITY].VirtualAddress;
+
+    if (!securityRva)
     {
         return CALG_SHA1;
     }
 
-    const PVOID pBase = pPeBytes + pImgDataDirectory[IMAGE_DIRECTORY_ENTRY_SECURITY].VirtualAddress;
+    if (securityRva > PeSize || (PeSize - securityRva) < sizeof(WIN_CERTIFICATE))
+    {
+        return CALG_SHA1;
+    }
+
+    const PVOID pBase = pPeBytes + securityRva;
     const LPWIN_CERTIFICATE pCert = (WIN_CERTIFICATE*)pBase;
+    const ULONG searchLen = min(pCert->dwLength, PeSize - securityRva);
     PUCHAR pMatch = NULL;
 
     if (NT_SUCCESS(DomitoMemorySearchPattern(
@@ -37,7 +46,7 @@ DomitoGetPortableExecutableDigestKind(
         0x00,
         15,
         pBase,
-        pCert->dwLength,
+        searchLen,
         (PVOID*)&pMatch
     )))
     {
@@ -49,7 +58,7 @@ DomitoGetPortableExecutableDigestKind(
         0xcc,
         19,
         pBase,
-        pCert->dwLength,
+        searchLen,
         (PVOID*)&pMatch
     )))
     {
@@ -99,6 +108,11 @@ DomitoCalculatePortableExecutableDigest(
     ULONG resultLength;
     ULONG fileOffset = 0;
 
+    if (PeSize < sizeof(IMAGE_DOS_HEADER))
+    {
+        return STATUS_INVALID_IMAGE_NOT_MZ;
+    }
+
     const PIMAGE_DOS_HEADER phDos = (IMAGE_DOS_HEADER*)pPeBytes;
     if (phDos->e_magic != IMAGE_DOS_SIGNATURE)
     {
@@ -106,6 +120,11 @@ DomitoCalculatePortableExecutableDigest(
         return STATUS_INVALID_IMAGE_NOT_MZ;
     }
 
+    if (phDos->e_lfanew > PeSize - sizeof(IMAGE_NT_HEADERS))
+    {
+        return STATUS_INVALID_IMAGE_FORMAT;
+    }
+
     const PIMAGE_NT_HEADERS phNt = (PIMAGE_NT_HEADERS)(pPeBytes + phDos->e_lfanew);
     if (phNt->Signature != IMAGE_NT_SIGNATURE)
     {
@@ -167,7 +186,7 @@ DomitoCalculatePortableExecutableDigest(
     //
     // Boring bcrypt boilerplate code
     //
-    const UINT32 peDigestKind = DomitoGetPortableExecutableDigestKind(pPeBytes, pImgDataDirectory);
+    const UINT32 peDigestKind = DomitoGetPortableExecutableDigestKind(pPeBytes, PeSize, pImgDataDirectory);
 
     if (!NT_SUCCESS(status = BCryptOpenAlgorithmProvider(
         &hbAlg,
@@ -275,9 +294,21 @@ DomitoCalculatePortableExecutableDigest(
     //
     // Now hash everything else in the file up to the certificate data.
     //
-    ULONG remaining = hasEmbeddedSig
-        ? pImgDataDirectory[IMAGE_DIRECTORY_ENTRY_SECURITY].VirtualAddress - fileOffset
-        : PeSize - fileOffset;
+    ULONG remaining;
+    if (hasEmbeddedSig)
+    {
+        const ULONG secRva = pImgDataDirectory[IMAGE_DIRECTORY_ENTRY_SECURITY].VirtualAddress;
+        if (secRva < fileOffset)
+        {
+            status = STATUS_INVALID_IMAGE_FORMAT;
+            goto cleanup;
+        }
+        remaining = secRva - fileOffset;
+    }
+    else
+    {
+        remaining = (fileOffset <= PeSize) ? (PeSize - fileOffset) : 0;
+    }
 
     while (remaining > 0)
     {
diff --git a/src/Domito.cpp b/src/Domito.cpp
index 73c43d3..41c9dab 100644
--- a/src/Domito.cpp
+++ b/src/Domito.cpp
@@ -213,7 +213,12 @@ DomitoMemorySearchPattern(
 
     *ppMatch = NULL;
 
-    for (SIZE_T i = 0; i < puSize - puLen; i++)
+    if (puLen == 0 || puSize < puLen)
+    {
+        return STATUS_NOT_FOUND;
+    }
+
+    for (SIZE_T i = 0; i + puLen <= puSize; i++)
     {
         BOOLEAN found = TRUE;
         for (SIZE_T j = 0; j < puLen; j++)