CVE-2021-29464: Out-of-bounds Write (CWE-787)
value: Exiv2 is a command-line utility and C++ library for reading, writing, deleting, and modifying the metadata of image files. A heap buffer overflow was found in Exiv2 versions v0.27.3 and earlier. The heap overflow is triggered when Exiv2 is used to write metadata into a crafted image file. An attacker could potentially exploit the vulnerability to gain code execution, if they can trick the victim into running Exiv2 on a crafted image file. Note that this bug is only triggered when writing the metadata, which is a less frequently used Exiv2 operation than reading the metadata. For example, to trigger the bug in the Exiv2 command-line application, you need to add an extra command-line argument such as `insert`. The bug is fixed in version v0.27.4.
CWE description: The product writes data past the end, or before the beginning, of the intended buffer.
CVSS v3 base score: 7.8
Published: 2021-04-30T19:15Z
Repository: https://github.com/Exiv2/exiv2
Language: C++
Files changed: src/jp2image.cpp
Commit date: 2021-04-20 21:19:51 +0200
Commit message: Better bounds checking in Jp2Image::encodeJp2Header()

Diff: diff --git a/src/jp2image.cpp b/src/jp2image.cpp
index 1661151b7..2689c4733 100644
--- a/src/jp2image.cpp
+++ b/src/jp2image.cpp
@@ -644,15 +644,15 @@ static void boxes_check(size_t b,size_t m)
 #endif
 
     void Jp2Image::encodeJp2Header(const DataBuf& boxBuf,DataBuf& outBuf)
     {
         DataBuf output(boxBuf.size_ + iccProfile_.size_ + 100); // allocate sufficient space
-        int     outlen = sizeof(Jp2BoxHeader) ; // now many bytes have we written to output?
-        int      inlen = sizeof(Jp2BoxHeader) ; // how many bytes have we read from boxBuf?
+        long    outlen = sizeof(Jp2BoxHeader) ; // now many bytes have we written to output?
+        long    inlen = sizeof(Jp2BoxHeader) ; // how many bytes have we read from boxBuf?
         Jp2BoxHeader* pBox   = (Jp2BoxHeader*) boxBuf.pData_;
-        int32_t       length = getLong((byte*)&pBox->length, bigEndian);
-        int32_t       count  = sizeof (Jp2BoxHeader);
+        uint32_t      length = getLong((byte*)&pBox->length, bigEndian);
+        uint32_t      count  = sizeof (Jp2BoxHeader);
         char*         p      = (char*) boxBuf.pData_;
         bool          bWroteColor = false ;
 
         while ( count < length || !bWroteColor ) {
             Jp2BoxHeader* pSubBox = (Jp2BoxHeader*) (p+count) ;
@@ -665,40 +665,44 @@ static void boxes_check(size_t b,size_t m)
                 subBox.length = getLong((byte*)&subBox.length, bigEndian);
                 subBox.type   = getLong((byte*)&subBox.type  , bigEndian);
 #ifdef EXIV2_DEBUG_MESSAGES
                 std::cout << "Jp2Image::encodeJp2Header subbox: "<< toAscii(subBox.type) << " length = " << subBox.length << std::endl;
 #endif
+                enforce(subBox.length <= length - count, Exiv2::kerCorruptedMetadata);
                 count        += subBox.length;
                 newBox.type   = subBox.type;
             } else {
                 subBox.length=0;
                 newBox.type = kJp2BoxTypeColorHeader;
                 count = length;
             }
 
-            int32_t newlen = subBox.length;
+            uint32_t newlen = subBox.length;
             if ( newBox.type == kJp2BoxTypeColorHeader ) {
                 bWroteColor = true ;
                 if ( ! iccProfileDefined() ) {
                     const char* pad   = "\x01\x00\x00\x00\x00\x00\x10\x00\x00\x05\x1cuuid";
                     uint32_t    psize = 15;
                     newlen            = sizeof(newBox) + psize ;
+                    enforce(newlen <= output.size_ - outlen, Exiv2::kerCorruptedMetadata);
                     ul2Data((byte*)&newBox.length,psize      ,bigEndian);
                     ul2Data((byte*)&newBox.type  ,newBox.type,bigEndian);
                     ::memcpy(output.pData_+outlen                     ,&newBox            ,sizeof(newBox));
                     ::memcpy(output.pData_+outlen+sizeof(newBox)      ,pad                ,psize         );
                 } else {
                     const char* pad   = "\x02\x00\x00";
                     uint32_t    psize = 3;
                     newlen            = sizeof(newBox) + psize + iccProfile_.size_;
+                    enforce(newlen <= output.size_ - outlen, Exiv2::kerCorruptedMetadata);
                     ul2Data((byte*)&newBox.length,newlen,bigEndian);
                     ul2Data((byte*)&newBox.type,newBox.type,bigEndian);
                     ::memcpy(output.pData_+outlen                     ,&newBox            ,sizeof(newBox)  );
                     ::memcpy(output.pData_+outlen+sizeof(newBox)      , pad               ,psize           );
                     ::memcpy(output.pData_+outlen+sizeof(newBox)+psize,iccProfile_.pData_,iccProfile_.size_);
                 }
             } else {
+                enforce(newlen <= output.size_ - outlen, Exiv2::kerCorruptedMetadata);
                 ::memcpy(output.pData_+outlen,boxBuf.pData_+inlen,subBox.length);
             }
 
             outlen += newlen;
             inlen  += subBox.length;

Vulnerable code:         int     outlen = sizeof(Jp2BoxHeader) ; // now many bytes have we written to output?
        int      inlen = sizeof(Jp2BoxHeader) ; // how many bytes have we read from boxBuf?
        int32_t       length = getLong((byte*)&pBox->length, bigEndian);
        int32_t       count  = sizeof (Jp2BoxHeader);
            int32_t newlen = subBox.length;
Fixed code:         long    outlen = sizeof(Jp2BoxHeader) ; // now many bytes have we written to output?
        long    inlen = sizeof(Jp2BoxHeader) ; // how many bytes have we read from boxBuf?
        uint32_t      length = getLong((byte*)&pBox->length, bigEndian);
        uint32_t      count  = sizeof (Jp2BoxHeader);
                enforce(subBox.length <= length - count, Exiv2::kerCorruptedMetadata);
            uint32_t newlen = subBox.length;
                    enforce(newlen <= output.size_ - outlen, Exiv2::kerCorruptedMetadata);
                    enforce(newlen <= output.size_ - outlen, Exiv2::kerCorruptedMetadata);
                enforce(newlen <= output.size_ - outlen, Exiv2::kerCorruptedMetadata);