CVE
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.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 1.1.0
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.1.0.
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 35/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
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.
Read the original 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.
Who should check
Teams running grpc_server (Hex, Erlang/Elixir elixir-grpc) 1.0.x that expose client-streaming or bidirectional-streaming RPC methods.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- Reach10/20Affects Hex packages
- Severity8.2/10CVSS 8.2
- No patch0/5No signal
What would change the score
- Would score about 80 if added to CISA KEV
- Would score about 75 if CISA's SSVC rates exploitation active
- Would score about 40 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 1.1.0.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
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"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- grpc_serverHex
From 1.0.0 · fixed in 1.1.0
- elixir-grpc/grpc
Version range not reported
- grpc_serverHex
From 1.0.0 · fixed in 1.1.0
Evidence 6
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-124279
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: cve.now feed data
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: github.com
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: cve.now feed data
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: github.com
How do I fix CVE-2026-124279?
Upgrade grpc_server to 1.1.0, the fixed version named in the advisory.Source: github.com