Summary
gRPC Erlang package has unbounded request body accumulation in readfullbody/3
'Elixir.GRPC.Server.Adapters.Cowboy.Handler':read_full_body/3 accumulates every received chunk into a single growing binary with no size cap. When the client omits the grpc-timeout header, the read timeout resolves to :infinity, allowing a slow-trickle attacker to hold the connection open indefinitely while memory grows. A single unauthenticated connection is sufficient to exhaust BEAM memory and crash the node.
Details
The read loop in lib/grpc/server/adapters/cowboy/handler.ex calls :cowboy_req.read_body/2 in a recursive loop, concatenating each chunk: body <> data. There is no running-total check and no configurable maximum body size. As the loop drains the receive buffer, cowboy issues fresh HTTP/2 WINDOW_UPDATE frames, so the client can keep pushing data indefinitely.
The grpc-timeout header is attacker-supplied and optional. When absent, timeout_left_opt(nil) returns :infinity, so the per-chunk read also has no deadline. The two missing controls compound: a fast client can blast multi-gigabyte payloads directly into memory; a slow client can trickle data forever.
PoC
- Start any
grpcserver exposing a unary RPC (no special configuration required). - Open an HTTP/2 connection and send a POST to any unary RPC path with
Content-Type: application/grpc+proto, omit thegrpc-timeoutheader. - Stream a large body (e.g. 1 GiB) in chunks without sending the final
END_STREAMflag immediately. - Observe BEAM memory growing proportionally to uploaded data with no server-side cap.
References
Impact
Affects grpc ≥ 0.3.1. No authentication, no special configuration, and no specific RPC method required, the unbounded read is on the default unary ingress path.
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-48854? CVE-2026-48854 is a high-severity allocation of resources without limits or throttling vulnerability in grpc (erlang), affecting versions >= 0.3.1, < 1.0.0. It is fixed in 1.0.0. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- Which versions of grpc are affected by CVE-2026-48854? grpc (erlang) versions >= 0.3.1, < 1.0.0 is affected.
- Is there a fix for CVE-2026-48854? Yes. CVE-2026-48854 is fixed in 1.0.0. Upgrade to this version or later.
- Is CVE-2026-48854 exploitable, and should I be worried? Whether CVE-2026-48854 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-48854 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-48854? Upgrade
grpcto 1.0.0 or later.