CVE-2021-29463 (published 2021-04-30T19:15Z)

Exiv2 is a command-line utility and C++ library for reading, writing, deleting, and modifying the metadata of image files. An out-of-bounds read was found in Exiv2 versions v0.27.3 and earlier. The out-of-bounds read is triggered when Exiv2 is used to write metadata into a crafted image file. An attacker could potentially exploit the vulnerability to cause a denial of service by crashing Exiv2, 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.

Severity: MEDIUM
CVSS v2 base score: 4.3 (AV:N/AC:M/Au:N/C:N/I:N/A:P)
CVSS v3 base score: 5.5, MEDIUM (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H)

Weakness information:
cwe_id: CWE-125
cwe_name: Out-of-bounds Read
description: The product reads data past the end, or before the beginning, of the intended buffer.
extended_description: 
            
            
             
			 
         
         

Fix information:
repo_url: https://github.com/Exiv2/exiv2
commit_details: repo_url: https://github.com/Exiv2/exiv2
author: Kevin Backhouse
author_date: 2021-04-19 18:06:00+01:00
msg: Improve bound checking in WebPImage::doWriteMetadata()
repository: repo_url: https://github.com/Exiv2/exiv2
repo_name: Exiv2/exiv2
description: Image metadata library and tools
repo_language: C++
owner: Exiv2
file_changes: filename: webpimage.cpp
change_type: ModificationType.MODIFY
diff: @@ -145,7 +145,7 @@ namespace Exiv2 {
         DataBuf chunkId(WEBP_TAG_SIZE+1);
         chunkId.pData_ [WEBP_TAG_SIZE] = '\0';
 
-        io_->read(data, WEBP_TAG_SIZE * 3);
+        readOrThrow(*io_, data, WEBP_TAG_SIZE * 3, Exiv2::kerCorruptedMetadata);
         uint64_t filesize = Exiv2::getULong(data + WEBP_TAG_SIZE, littleEndian);
 
         /* Set up header */
@@ -185,13 +185,20 @@ namespace Exiv2 {
          case we have any exif or xmp data, also check
          for any chunks with alpha frame/layer set */
         while ( !io_->eof() && (uint64_t) io_->tell() < filesize) {
-            io_->read(chunkId.pData_, WEBP_TAG_SIZE);
-            io_->read(size_buff, WEBP_TAG_SIZE);
-            long size = Exiv2::getULong(size_buff, littleEndian);
+            readOrThrow(*io_, chunkId.pData_, WEBP_TAG_SIZE, Exiv2::kerCorruptedMetadata);
+            readOrThrow(*io_, size_buff, WEBP_TAG_SIZE, Exiv2::kerCorruptedMetadata);
+            const uint32_t size_u32 = Exiv2::getULong(size_buff, littleEndian);
+
+            // Check that `size_u32` is safe to cast to `long`.
+            enforce(size_u32 <= static_cast<size_t>(std::numeric_limits<unsigned int>::max()),
+                    Exiv2::kerCorruptedMetadata);
+            const long size = static_cast<long>(size_u32);
             DataBuf payload(size);
-            io_->read(payload.pData_, payload.size_);
-            byte c;
-            if ( payload.size_ % 2 ) io_->read(&c,1);
+            readOrThrow(*io_, payload.pData_, payload.size_, Exiv2::kerCorruptedMetadata);
+            if ( payload.size_ % 2 ) {
+              byte c;
+              readOrThrow(*io_, &c, 1, Exiv2::kerCorruptedMetadata);
+            }
 
             /* Chunk with information about features
              used in the file. */
@@ -199,6 +206,7 @@ namespace Exiv2 {
                 has_vp8x = true;
             }
             if (equalsWebPTag(chunkId, WEBP_CHUNK_HEADER_VP8X) && !has_size) {
+                enforce(size >= 10, Exiv2::kerCorruptedMetadata);
                 has_size = true;
                 byte size_buf[WEBP_TAG_SIZE];
 
@@ -227,6 +235,7 @@ namespace Exiv2 {
             }
 #endif
             if (equalsWebPTag(chunkId, WEBP_CHUNK_HEADER_VP8) && !has_size) {
+                enforce(size >= 10, Exiv2::kerCorruptedMetadata);
                 has_size = true;
                 byte size_buf[2];
 
@@ -244,11 +253,13 @@ namespace Exiv2 {
 
             /* Chunk with with lossless image data. */
             if (equalsWebPTag(chunkId, WEBP_CHUNK_HEADER_VP8L) && !has_alpha) {
+                enforce(size >= 5, Exiv2::kerCorruptedMetadata);
                 if ((payload.pData_[4] & WEBP_VP8X_ALPHA_BIT) == WEBP_VP8X_ALPHA_BIT) {
                     has_alpha = true;
                 }
             }
             if (equalsWebPTag(chunkId, WEBP_CHUNK_HEADER_VP8L) && !has_size) {
+                enforce(size >= 5, Exiv2::kerCorruptedMetadata);
                 has_size = true;
                 byte size_buf_w[2];
                 byte size_buf_h[3];
@@ -276,11 +287,13 @@ namespace Exiv2 {
 
             /* Chunk with animation frame. */
             if (equalsWebPTag(chunkId, WEBP_CHUNK_HEADER_ANMF) && !has_alpha) {
+                enforce(size >= 6, Exiv2::kerCorruptedMetadata);
                 if ((payload.pData_[5] & 0x2) == 0x2) {
                     has_alpha = true;
                 }
             }
             if (equalsWebPTag(chunkId, WEBP_CHUNK_HEADER_ANMF) && !has_size) {
+                enforce(size >= 12, Exiv2::kerCorruptedMetadata);
                 has_size = true;
                 byte size_buf[WEBP_TAG_SIZE];
 
@@ -309,16 +322,22 @@ namespace Exiv2 {
 
         io_->seek(12, BasicIo::beg);
         while ( !io_->eof() && (uint64_t) io_->tell() < filesize) {
-            io_->read(chunkId.pData_, 4);
-            io_->read(size_buff, 4);
+            readOrThrow(*io_, chunkId.pData_, 4, Exiv2::kerCorruptedMetadata);
+            readOrThrow(*io_, size_buff, 4, Exiv2::kerCorruptedMetadata);
+
+            const uint32_t size_u32 = Exiv2::getULong(size_buff, littleEndian);
 
-            long size = Exiv2::getULong(size_buff, littleEndian);
+            // Check that `size_u32` is safe to cast to `long`.
+            enforce(size_u32 <= static_cast<size_t>(std::numeric_limits<unsigned int>::max()),
+                    Exiv2::kerCorruptedMetadata);
+            const long size = static_cast<long>(size_u32);
 
             DataBuf payload(size);
-            io_->read(payload.pData_, size);
+            readOrThrow(*io_, payload.pData_, size, Exiv2::kerCorruptedMetadata);
             if ( io_->tell() % 2 ) io_->seek(+1,BasicIo::cur); // skip pad
 
             if (equalsWebPTag(chunkId, WEBP_CHUNK_HEADER_VP8X)) {
+                enforce(size >= 1, Exiv2::kerCorruptedMetadata);
                 if (has_icc){
                     payload.pData_[0] |= WEBP_VP8X_ICC_BIT;
                 } else {

programming_language: C++