Autobahn Python is a WebSocket and WAMP implementation for Python that supports Twisted and asyncio. Prior to 26.7.1, WebSocket endpoints that accept permessage-deflate and rely on maxMessagePayloadSize enforce that limit against the compressed frame length before inflation but do not recheck the decompressed message size before delivery. A remote unauthenticated client can send a valid compressed frame below the configured wire-size limit that expands beyond the application message limit, causing oversized data to be allocated, joined, validated, and passed to application callbacks. This can create resource-exhaustion pressure, but the advisory does not establish confidentiality or integrity impact. This issue is fixed in version 26.7.1.
CVE-2026-77528
MEDIUMPre-NVD 5.35.3
EchelonGraph scoreLOW confidence
This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: secondary
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 5.3Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 5.3
- EG Score
- 5.3(low)
- EG Risk
- 28(Track)EG Risk 28/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity53% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- —
- EPSS %ILE
- —
- KEV
- Not listed
Published
September 18, 2026
Last Modified
September 18, 2026
Advisory Details (4)
Auto-updated Sep 18, 2026🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available
Release v26_7_1
Patch available: crossbario/autobahn-python v26_7_1
https://github.com/crossbario/autobahn-python/releases/tag/v26_7_1github_commit
commit 77d323a30b09 (crossbario/autobahn-python)
Fix landed in crossbario/autobahn-python commit 77d323a30b09 — awaiting tagged release
https://github.com/crossbario/autobahn-python/commit/77d323a30b09b1828ad8be2ce6344e056970e613github_pr
Fix 1909
Fix merged in crossbario/autobahn-python PR #1916 on 2026-07-14 — awaiting tagged release
https://github.com/crossbario/autobahn-python/pull/1916github Patch Available🟡 PoC Available
Autobahn Python permessage-deflate bypasses maxMessagePayloadSize after inflation · Advisory · crossbario/autobahn-python · GitHub
https://github.com/crossbario/autobahn-python/security/advisories/GHSA-hxp9-w8x3-p566Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 3× in last 7d / 3× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-09-18 20:30 UTCEG score recompute
- 2026-09-18 19:49 UTCEG score recompute
- 2026-09-18 19:49 UTCMITRE cvelistV5first tracked
Frequently asked(4)
What is CVE-2026-77528?
CVE-2026-77528 is a medium vulnerability published on September 18, 2026. Autobahn Python is a WebSocket and WAMP implementation for Python that supports Twisted and asyncio. Prior to 26.7.1, WebSocket endpoints that accept permessage-deflate and rely on maxMessagePayloadSize enforce that limit against the compressed frame length before inflation but do not recheck the…
When was CVE-2026-77528 disclosed?
CVE-2026-77528 was first published in the National Vulnerability Database on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-77528?
CVE-2026-77528 has a CVSS v3 base score of 5.3 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-77528?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77528, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-77528
Is Your Infrastructure Affected by CVE-2026-77528?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.