Unauthenticated service interruption via quadratic WebSocket reassembly
Published Jul 24, 2026 · Updated Jul 24, 2026
Inefficient algorithmic complexity in Bandit 1.11.0 through 1.12.0 allows remote attackers to interrupt service via WebSocket frames. The WebSocket connection handler nests each continuation payload in an iolist and repeatedly traverses the full buffer with IO.iodata_length/1, producing quadratic work. Any unauthenticated client able to open a Bandit WebSocket can pin a scheduler with many tiny fragments, and concurrent connections can starve the server.
Summary
What happened
Inefficient algorithmic complexity in Bandit 1.11.0 through 1.12.0 allows remote attackers to interrupt service via WebSocket frames. The WebSocket connection handler nests each continuation payload in an iolist and repeatedly traverses the full buffer with IO.iodata_length/1, producing quadratic work. Any unauthenticated client able to open a Bandit WebSocket can pin a scheduler with many tiny fragments, and concurrent connections can starve the server.
The record
- CVE
- CVE-2026-65623
- Published
- Jul 24, 2026
- Updated
- Jul 24, 2026
- Vendor
- Mat Trudel
- Product
- Bandit
- Classifications
- CWE-407, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 24, 2026CVE publishedPublication date reported by the CVE source.
- Jul 24, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.11.0 <1.12.1
- Affected versionversion=21612c7c7b1ce43eccd36d3af3a2299d23513667 <418ef7e906192a230ddba112f7a669c87b6b0e3a
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-vg8x-66vg-5pxh WebSocket fragmentation proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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