Vulnerability in autobahn (CVE-2026-77528)
Summary
Vulnerability in autobahn (CVE-2026-77528). Risk of unauthorized operations or information disclosure. Exploitable via maxMessagePayloadSize. Mitigation: upgrade to 26.7.1 or later.
Original description
The description as published by the source.
Summary
Autobahn Python enforces maxMessagePayloadSize against the compressed WebSocket frame length before permessage-deflate inflation, then delivers the inflated message to application callbacks without a second size check. A client frame that is only 22 compressed bytes can inflate to 4096 bytes and reach onMessage even when the application configured a 128-byte message limit, defeating the resource boundary the option is meant to provide.
Details
The permessage-deflate path installs a PerMessageDeflate instance when the server accepts a client offer in src/autobahn/websocket/protocol.py:3371. The common PerMessageDeflateOfferAccept(offer) path leaves max_message_size at its default None in src/autobahn/websocket/compress_deflate.py:295, and that value is copied into the compressor object in src/autobahn/websocket/compress_deflate.py:723. When a data frame arrives with RSV1 set, Autobahn marks the message compressed in src/autobahn/websocket/protocol.py:1812, calls onMessageFrameBegin with the compressed frame length, and increments message_data_total_length by that pre-inflate length in src/autobahn/websocket/protocol.py:634; the configured message cap is enforced against the same compressed accounting at src/autobahn/websocket/protocol.py:636. Only after those checks does Autobahn inflate the payload in src/autobahn/websocket/protocol.py:1861; because max_message_size is None, src/autobahn/websocket/compress_deflate.py:812 ca…
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-2026-77528 has been found in autobahn.
Attackers can target a specific entry point like maxMessagePayloadSize over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade autobahn to 26.7.1 or later.
If unsure, ask your IT team or search "autobahn CVE-2026-77528" on the vendor's site.
CVE-2026-77528 (autobahn) — CWE-409 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: maxMessagePayloadSize / onMessage / PerMessageDeflate / max_message_size
Patched: 26.7.1 — 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-409) exists in autobahn. Attackers reach the vulnerable code path via maxMessagePayloadSize without authentication.
Check the vendor advisory for the affected versions of autobahn. Attack surface: maxMessagePayloadSize / onMessage / PerMessageDeflate / max_message_size.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 26.7.1.
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 'autobahn' . 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
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1Identify exposure identify
grep -r 'autobahn' . | 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
autobahn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 autobahn to 26.7.1ステージング環境で 26.7.1 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-2026-77528 python-autobahn
References
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- package pypi.org
- package pypi.org
- web github.com
- web github.com
- web github.com
- web github.com