Vulnerability in granian (CVE-2026-42544)
Summary
Vulnerability in granian (CVE-2026-42544). Risk of unauthorized operations or information disclosure. Exploitable via Err. Mitigation: upgrade to 2.7.4 or later.
Original description
The description as published by the source.
Summary
Granian aborts a worker process when an unauthenticated client sends a WebSocket upgrade request whose Sec-WebSocket-Protocol header contains non-ASCII bytes.
The crash happens in Granian's WebSocket scope construction path, before the ASGI application is invoked.
This is a single-request Denial Of Service against one worker. Repeating the request across workers takes the service offline.
Details
HeaderValue::to_str() returns Err for bytes outside visible ASCII. The subsequent .unwrap() panics.
In release builds Granian sets panic = "abort", so this panic terminates the worker instead of being handled as a normal request error.
PoC
Step 1.
starts a Granian ASGI server
# app.py
async def app(scope, receive, send):
if scope["type"] == "websocket":
await receive()
await send({"type": "websocket.accept"})
return
await send({"type": "http.response.start", "status": 200, "headers": []})
await send({"type": "http.response.body", "body": b"ok"})
granian --interface asgi app:app --host 127.0.0.1 --port 8000
Step 2.
sending a raw upgrade request with Sec-WebSocket-Protocol: \x80\xff reached this code path and caused the worker to abort.
# ws-subproto-crash.py
import base64, os, socket, sys
host, port, path = sys.argv[1], int(sys.argv[2]), sys.…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-42544 has been found in granian.
Attackers can target a specific entry point like Err over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade granian to 2.7.4 or later.
If unsure, ask your IT team or search "granian CVE-2026-42544" on the vendor's site.
CVE-2026-42544 (granian) — CWE-20 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Err
Patched: 2.7.4 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-20) exists in granian. Attackers reach the vulnerable code path via Err without authentication.
Check the vendor advisory for the affected versions of granian. Attack surface: Err.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 2.7.4.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'granian' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'granian' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
granianを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade granian to 2.7.4ステージング環境で 2.7.4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com