CVE-2026-77528 json
Autobahn Python permessage-deflate bypasses maxMessagePayloadSize after inflation
published 2026-09-18 51 d ago modified 2026-10-01 38 d ago also GHSA-hxp9-w8x3-p566 , PYSEC-2026-4027 , PYSEC-2026-4031 , EUVD-2026-83415
- cvss
- 5.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 44%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- pypi autobahn 26.7.1
- pypi crossbar 26.7.1
- python-autobahn openSUSE Tumbleweed 26.7.1-2.1
opensuse advisories openSUSE-SU-2026:11852-1
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 50 d ago
Exploit prediction
0.52% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| GitHub | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| OSV | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | autobahn | <26.7.1 |
26.7.1 |
| pypi | crossbar | <26.7.1 |
26.7.1 |
Affected products
- crossbario autobahn-python
Classification
References
-
github.com
/crossbario/autobahn-python/pull/1916
web
-
github.com
/crossbario/autobahn-python/commit/77d323a30b09b1828ad8be2ce6344e056970e613
web
-
github.com
/crossbario/autobahn-python/security/advisories/GHSA-hxp9-w8x3-p566
web
-
github.com
/crossbario/autobahn-python/releases/tag/v26_7_1
web
-
nvd.nist.gov
/vuln/detail/CVE-2026-77528
advisory
-
github.com
/crossbario/autobahn-python
package
-
pypi.org
/project/crossbar
package
-
github.com
/advisories/GHSA-hxp9-w8x3-p566
advisory
-
pypi.org
/project/autobahn
package
Sources
- CVE List CVE-2026-77528
- GitHub Advisory GHSA-hxp9-w8x3-p566
- NVD CVE-2026-77528
- OSV PYSEC-2026-4031
- OSV PYSEC-2026-4027
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.