elixir-grpc CVE-2026-48853
CRITICALSeverity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-reachable and unauthenticated, but the server must register the erlpack codec and RCE requires a downstream apply site, justifying AC:H; full C/I/A impact on the BEAM node.
Primary rating from Vendor (EEF).
CVSS VectorVendor: EEF
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
2DescriptionCVE.org
Deserialization of Untrusted Data and Allocation of Resources Without Limits or Throttling vulnerabilities in elixir-grpc grpc allow unauthenticated attackers to crash the BEAM node via atom table exhaustion and, when a decoded term flows into a call site that invokes it, achieve remote code execution on the server.
'Elixir.GRPC.Codec.Erlpack':decode/2 (lib/grpc/codec/erlpack.ex) calls :erlang.binary_to_term/1 on the raw gRPC message body without the :safe option, no size bound, and no type guard. Any unauthenticated peer that sends a request with Content-Type: application/grpc+erlpack can send a crafted payload that mints arbitrary new atoms (which are never garbage-collected, exhausting the bounded atom table and crashing the VM) or that encodes a fun term which, if applied anywhere downstream, executes attacker-controlled code inside the server process.
This issue affects grpc from 0.4.0 before 1.0.0.
AnalysisAI
Unsafe Erlang term deserialization in the elixir-grpc library (versions 0.4.0 through 1.0.0) allows unauthenticated remote attackers to crash the BEAM VM via atom-table exhaustion or achieve remote code execution by sending crafted gRPC payloads with Content-Type application/grpc+erlpack. The flaw lives in GRPC.Codec.Erlpack.decode/2, which calls :erlang.binary_to_term/1 without the :safe option, size bounds, or type guards. No public exploit is identified at time of analysis, but the upstream fix is published at commit 272a97a and a patched 1.0.0 release is available.
Technical ContextAI
The elixir-grpc project is an Elixir/Erlang implementation of gRPC that runs on the BEAM virtual machine. The vulnerable codec module lib/grpc/codec/erlpack.ex uses Erlang's External Term Format via :erlang.binary_to_term/1, a known-dangerous API documented by the Erlang Ecosystem Foundation (EEF) - the reporter here - as unsafe for untrusted input. Without the :safe atom, attackers can mint new atoms (BEAM's atom table is bounded, typically 1,048,576 entries, and atoms are never garbage-collected) or encode fun terms, pids, ports, and references. The root cause is CWE-502 (Deserialization of Untrusted Data), compounded by CWE-770 (Allocation of Resources Without Limits or Throttling). When a decoded fun term flows into any call site that applies it (e.g., :erlang.apply/2 or anonymous-function invocation), the attacker-controlled closure executes inside the gRPC server process.
RemediationAI
Vendor-released patch: upgrade the elixir-grpc grpc Hex dependency to 1.0.0 or later, which contains the fix landed in commit 272a97a5ea1b46af1819f14a831fcf35fc91f992 (see https://github.com/elixir-grpc/grpc/commit/272a97a5ea1b46af1819f14a831fcf35fc91f992 and the advisory at https://github.com/elixir-grpc/grpc/security/advisories/GHSA-grp7-v8xh-rj7h). If immediate upgrade is not possible, remove or unregister the Erlpack codec from your gRPC server's accepted codecs so requests with Content-Type application/grpc+erlpack are rejected - the trade-off is that any legitimate internal clients relying on the erlpack wire format will break and must move to protobuf or JSON. As a network-layer compensating control, terminate gRPC behind a reverse proxy or service mesh that strips or rejects application/grpc+erlpack content types, accepting that this requires Layer-7 inspection and may add latency. Increasing the BEAM +t atom-table limit only delays the DoS and does nothing to mitigate the RCE path, so it is not a sufficient standalone mitigation.
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Same weakness CWE-502 – Deserialization of Untrusted Data
View allSame technique Deserialization
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