Vulnerability in cowboy (CVE-2026-65624)
Summary
Vulnerability in cowboy (CVE-2026-65624). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 2.18.0 or later.
Original description
The description as published by the source.
Summary
Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows an unauthenticated remote attacker to exhaust connection process memory over HTTP/1.1.
The HTTP/1.1 handler in cowboy_http enforces the max_headers limit by counting the number of distinct header names in a map (maps:size(Headers)). When a request contains multiple header lines with the same name, the values are concatenated into a single ever-growing binary stored under that one map key (", " for regular headers, "; " for cookies), so the map size stays at one and the max_headers cap (default 100) is never reached. Because no accumulator bounds the total number of header lines or the total byte size of the header block (only per-line max_header_name_length and max_header_value_length apply), an unauthenticated client can send an arbitrary number of header lines with the same name and grow the connection process's binary memory to arbitrary size within the request window.
The impact per connection is bounded by request_timeout (default 5 seconds, not reset by header data), and by max_heap_size when set (the offending connection process is killed once its heap grows past the limit). When max_heap_size is left at the default (unset), sustained abuse can drive the Erlang VM into out-of-memory conditions.
This issue affects cowboy from 2.0.0-pre.4 before 2.18.0.
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-2026-65624 has been found in cowboy.
Risk of unauthorized operations or information disclosure.
What to do: upgrade cowboy to 2.18.0 or later.
If unsure, ask your IT team or search "cowboy CVE-2026-65624" on the vendor's site.
CVE-2026-65624 (cowboy) — CWE-770
Patched: 2.18.0 — 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-770) exists in cowboy.
Check the vendor advisory for the affected versions of cowboy.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 2.18.0.
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 'cowboy' . 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 'cowboy' . | 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
cowboy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 cowboy to 2.18.0ステージング環境で 2.18.0 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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-65624 erlang-cowboy Fixed in: 2.18.0+dfsg-1
- Ubuntu UBUNTU-CVE-2026-65624 rabbitmq-server
References
- package hex.pm
- patch github.com
- web cna.erlef.org
- web osv.dev
- web nvd.nist.gov
- web github.com