CVE-2022-46149 (published 2022-11-30T17:15Z)

Cap'n Proto is a data interchange format and remote procedure call (RPC) system. Cap'n Proro prior to versions 0.7.1, 0.8.1, 0.9.2, and 0.10.3, as well as versions of Cap'n Proto's Rust implementation prior to 0.13.7, 0.14.11, and 0.15.2 are vulnerable to out-of-bounds read due to logic error handling list-of-list. This issue may lead someone to remotely segfault a peer by sending it a malicious message, if the victim performs certain actions on a list-of-pointer type. Exfiltration of memory is possible if the victim performs additional certain actions on a list-of-pointer type. To be vulnerable, an application must perform a specific sequence of actions, described in the GitHub Security Advisory. The bug is present in inlined code, therefore the fix will require rebuilding dependent applications. Cap'n Proto has C++ fixes available in versions 0.7.1, 0.8.1, 0.9.2, and 0.10.3. The `capnp` Rust crate has fixes available in versions 0.13.7, 0.14.11, and 0.15.2.

CVSS v3 base score: 5.4, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L)

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/capnproto/capnproto
commit_details: repo_url: https://github.com/capnproto/capnproto
author: Kenton Varda
author_date: 2022-11-23 12:02:29-06:00
msg: Apply data offset for list-of-pointers at access time rather than ListReader creation time.

Baking this offset into `ptr` reduced ops needed at access time but made the interpretation of `ptr` inconsistent depending on what type of list was expected.
repository: repo_url: https://github.com/capnproto/capnproto
repo_name: capnproto/capnproto
description: Cap'n Proto serialization/RPC system - core tools and C++ library
repo_language: C++
owner: capnproto
file_changes: filename: layout.c++
change_type: ModificationType.MODIFY
diff: @@ -2360,10 +2360,6 @@ struct WireHelpers {
             break;
 
           case ElementSize::POINTER:
-            // We expected a list of pointers but got a list of structs.  Assuming the first field
-            // in the struct is the pointer we were looking for, we want to munge the pointer to
-            // point at the first element's pointer section.
-            ptr += tag->structRef.dataSize.get();
             KJ_REQUIRE(tag->structRef.ptrCount.get() > ZERO * POINTERS,
                        "Schema mismatch: Expected a pointer list, but got a list of data-only "
                        "structs.") {

programming_language: C++
filename: layout.h
change_type: ModificationType.MODIFY
diff: @@ -1227,8 +1227,12 @@ inline Void ListReader::getDataElement<Void>(ElementCount index) const {
 }
 
 inline PointerReader ListReader::getPointerElement(ElementCount index) const {
+  // If the list elements have data sections we need to skip those. Note that for pointers to be
+  // present at all (which already must be true if we get here), then `structDataSize` must be a
+  // whole number of words, so we don't have to worry about unaligned reads here.
+  auto offset = structDataSize / BITS_PER_BYTE;
   return PointerReader(segment, capTable, reinterpret_cast<const WirePointer*>(
-      ptr + upgradeBound<uint64_t>(index) * step / BITS_PER_BYTE), nestingLimit);
+      ptr + offset + upgradeBound<uint64_t>(index) * step / BITS_PER_BYTE), nestingLimit);
 }
 
 // -------------------------------------------------------------------

programming_language: C++