CVE-2026-77528Autobahn Python permessage-deflate bypasses maxMessagePayloadSize after inflation
- 5.3MediumCVSS base score
- 0.52%Exploitation in 30 daysEPSS · top 55% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
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.
Timeline
ID reserved
By GitHub_M
- 29 days later
· 29 days later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| NVDNVD · Deferred | 3.1 | Medium5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
- EPSS (exploitation in 30 days)
- 0.52% · top 55% of all CVEs (15 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.
Affected products
- affected < 26.7.1
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPIautobahnGHSA-hxp9-w8x3-p566 (opens in a new tab)
- PyPIcrossbarGHSA-hxp9-w8x3-p566 (opens in a new tab)
References
References4
- https://github.com/crossbario/autobahn-python/security/advisories/GHSA-hxp9-w8x3-p566 (opens in a new tab)x_refsource_CONFIRM
- https://github.com/crossbario/autobahn-python/pull/1916 (opens in a new tab)x_refsource_MISC
- https://github.com/crossbario/autobahn-python/commit/77d323a30b09b1828ad8be2ce6344e056970e613 (opens in a new tab)x_refsource_MISC
- https://github.com/crossbario/autobahn-python/releases/tag/v26_7_1 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-83415 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-hxp9-w8x3-p566 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-77528)Record last updated .