CVE-2026-104635Uncontrolled recursion in elixir-protobuf/protobuf JSON decoding of self-referential messages

Official description

Uncontrolled Recursion vulnerability in Protobuf.JSON.Decode in elixir-protobuf protobuf allows an unauthenticated remote attacker to crash the decoding process via a deeply nested JSON document. Any application that decodes attacker-supplied JSON with Protobuf.JSON.decode/3, Protobuf.JSON.decode!/3, or Protobuf.JSON.from_decoded/3 into a schema that contains a self-referential or cyclic message type is affected. In lib/protobuf/json/decode.ex, the embedded-message clause of decode_singular/3 recurses into internal_from_json_data/3 once per nesting level without incrementing or checking the decoder's depth counter. The depth guard increase_depth_and_maybe_throw/1 covers only the Google.Protobuf.ListValue and Google.Protobuf.Struct clauses, so the recursion_limit option has no effect on user-defined message types. Each nesting level allocates a stack frame and heap objects, and a sufficiently deep document exhausts the memory of the decoding process. Confidentiality and integrity are not affected. This issue affects protobuf: from 0.8.0 before 0.17.1.

Affected packages & fixed versions

Affected products (as reported)

References

• GitHub Advisory related, vendor-advisory
• EEF CNA record for CVE-2026-104635 related
• OSV record EEF-CVE-2026-104635 related
• Introducing commit b0a1d4e in elixir-protobuf/protobuf related
• Fix commit e9432ad in elixir-protobuf/protobuf patch