CVE-2020-26243

Nanopb is a small code-size Protocol Buffers implementation. In Nanopb
before versions 0.4.4 and 0.3.9.7, decoding specifically formed message can
leak memory if dynamic allocation is enabled and an oneof field contains a
static submessage that contains a dynamic field, and the message being
decoded contains the submessage multiple times. This is rare in normal
messages, but it is a concern when untrusted data is parsed. This is fixed
in versions 0.3.9.7 and 0.4.4. The following workarounds are available: 1)
Set the option no_unions for the oneof field. This will generate fields
as separate instead of C union, and avoids triggering the problematic code.
2) Set the type of the submessage field inside oneof to FT_POINTER. This
way the whole submessage will be dynamically allocated and the problematic
code is not executed. 3) Use an arena allocator for nanopb, to make sure
all memory can be released afterwards.

Bugs

• <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=975838&gt;