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CVE-2026-77528

Autobahn Python permessage-deflate bypasses maxMessagePayloadSize after inflation

CVSS 3.1 5.3 MEDIUMCheck source for fixed versionsKEV status unknown
Original advisory

cve-program · CVE-2026-77528

Published

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.

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Affected versions, risk and source history

Exploitation and risk

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cve-program · CVE-2026-77528

Published

Autobahn Python permessage-deflate bypasses maxMessagePayloadSize after inflation

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.

Source published
18 Sep 2026 19:42:18 UTC
Source modified
19 Sep 2026 14:11:38 UTC
Saved here
23 Oct 2026 15:48:27 UTC
Source terms
CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 3.1 · 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

ChangeIntel

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Sources read 13 Nov 01:58 UTC · 274 of 275 readable · 272 fully read · documentation 464/469 current

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