CVE-2026-77528Autobahn Python permessage-deflate bypasses maxMessagePayloadSize after inflation
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Weakness (CWE)
- CWE-409, CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Sep 19, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
crossbario autobahn-python crossbario:autobahn_python (from the name) | before 26.7.1 | CNA record |
References
- https://github.com/crossbario/autobahn-python/security/advisories/GHSA-hxp9-w8x3-p566x-refsource-confirm
- https://github.com/crossbario/autobahn-python/pull/1916x-refsource-misc
- https://github.com/crossbario/autobahn-python/commit/77d323a30b09b1828ad8be2ce6344e056970e613x-refsource-misc
- https://github.com/crossbario/autobahn-python/releases/tag/v26_7_1x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.