Fix CVE-2025-2153

release_docs/CHANGELOG.md

@@ -495,6 +495,12 @@ Simple example programs showing how to use complex number datatypes have been ad
 
 ## Library
 
+### Fixed security issue CVE-2025-2153
+
+   The message flags field could be modified such that a message that is not sharable according to the share_flags field in H5O_msg_class_t can be treated as sharable. An assert has been added in H5O__msg_write_real to make sure messages that are not sharable can't be modified to shared. Additionally, the check in H5O__chunk_deserialize that catches unsharable messages being marked as sharable has been improved.
+
+   Fixes GitHub issue #5329
+
 ### Fixed security issue CVE-2025-6857
 
    An HDF5 file had a corrupted v1 B-tree that would result in a stack overflow when performing a lookup on it. This has been fixed with additional integrity checks.

src/H5Ocache.c

@@ -1403,8 +1403,8 @@ H5O__chunk_deserialize(H5O_t *oh, haddr_t addr, size_t chunk_size, const uint8_t
             else {
                 /* Check for message of unshareable class marked as "shareable"
                  */
-                if ((flags & H5O_MSG_FLAG_SHAREABLE) && H5O_msg_class_g[id] &&
-                    !(H5O_msg_class_g[id]->share_flags & H5O_SHARE_IS_SHARABLE))
+                if (((flags & H5O_MSG_FLAG_SHARED) || (flags & H5O_MSG_FLAG_SHAREABLE)) &&
+                    H5O_msg_class_g[id] && !(H5O_msg_class_g[id]->share_flags & H5O_SHARE_IS_SHARABLE))
                     HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL,
                                 "message of unshareable class flagged as shareable");
 

src/H5Omessage.c

@@ -354,6 +354,9 @@ H5O__msg_write_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type, unsigned m
          */
         assert(!(mesg_flags & H5O_MSG_FLAG_DONTSHARE));
 
+        /* Sanity check to see if the type is not sharable */
+        assert(type->share_flags & H5O_SHARE_IS_SHARABLE);
+
         /* Remove the old message from the SOHM index */
         /* (It would be more efficient to try to share the message first, then
          *      delete it (avoiding thrashing the index in the case the ref.