Client memory exhaustion via unbounded chunk-size buffering
Published Sep 29, 2026 · Updated Sep 29, 2026
Denial of service in urllib3 1.10.3 through 2.7.0 allows remote attackers to exhaust client memory via a chunked HTTP response. The HTTPResponse.read_chunked() and stream() parser buffers a chunk-size line until newline or EOF without a length limit, even when the line is invalid. Exposure requires an application to stream a chunked response from an untrusted HTTP server; memory exhaustion can crash the client process.
Summary
What happened
Denial of service in urllib3 1.10.3 through 2.7.0 allows remote attackers to exhaust client memory via a chunked HTTP response. The HTTPResponse.read_chunked() and stream() parser buffers a chunk-size line until newline or EOF without a length limit, even when the line is invalid. Exposure requires an application to stream a chunked response from an untrusted HTTP server; memory exhaustion can crash the client process.
The record
- CVE
- CVE-2026-97689
- Published
- Sep 29, 2026
- Updated
- Sep 29, 2026
- Vendor
- urllib3
- Product
- urllib3
- Classifications
- CWE-770, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 29, 2026CVE publishedPublication date reported by the CVE source.
- Sep 29, 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=>= 1.10.3, < 2.8.0
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.
Activity data is delayed. The latest report is Sep 28, 2026.
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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