Service interrupt via quadratic chunk-boundary removal
Published Jan 5, 2026 · Updated Jan 5, 2026
Denial of service in aio-libs aiohttp before 3.13.3 allows remote attackers to interrupt service with many small HTTP chunks. StreamReader stores each chunk boundary in _http_chunk_splits and previously removed leading entries from a list with repeated pop(0) operations, making request.read() consume blocking CPU as chunk count grows. Exploitation requires an endpoint that calls request.read(); the event loop cannot serve other requests during the resulting processing delay.
Summary
What happened
Denial of service in aio-libs aiohttp before 3.13.3 allows remote attackers to interrupt service with many small HTTP chunks. StreamReader stores each chunk boundary in _http_chunk_splits and previously removed leading entries from a list with repeated pop(0) operations, making request.read() consume blocking CPU as chunk count grows. Exploitation requires an endpoint that calls request.read(); the event loop cannot serve other requests during the resulting processing delay.
The record
- CVE
- CVE-2025-69229
- Published
- Jan 5, 2026
- Updated
- Jan 5, 2026
- Vendor
- aio-libs
- Product
- aiohttp
- Classifications
- CWE-770, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 5, 2026CVE publishedPublication date reported by the CVE source.
- Jan 5, 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=< 3.13.3
What conditions does exploitation require?
What is affected?
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
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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