CVE-2026-104635 — elixir-protobuf / protobuf
Uncontrolled RecursionUncontrolled 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.
| Software | Affected versions |
|---|---|
| elixir-protobuf / protobuf | >= 0.8.0, < 0.17.1 |
- https://cna.erlef.org/cves/CVE-2026-104635.html
- https://github.com/elixir-protobuf/protobuf/commit/b0a1d4eaffaf50012fa71a8e931a47cf252d0370
- https://github.com/elixir-protobuf/protobuf/commit/e9432ad1c4099511905353cebcececa3a1f7c3ff
- https://github.com/elixir-protobuf/protobuf/security/advisories/GHSA-m497-c2h9-rvw6
- https://osv.dev/vulnerability/EEF-CVE-2026-104635
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A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
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