Client memory exhaustion via queued automatic PONGs
Published Jul 3, 2026 · Updated Jul 3, 2026
Resource exhaustion in curl 8.16.0 through 8.20.0 allows remote attackers controlling a WebSocket server to exhaust client memory. In lib/ws.c, automatic PONG handling queues each response into the WebSocket send buffer even when the server does not read acknowledgments, so sequential PING frames drive unbounded allocation. A target must initiate a WebSocket transfer to the malicious server with automatic PONG responses enabled; sustained flooding can return an out-of-memory error or starve the surrounding application.
Summary
What happened
Resource exhaustion in curl 8.16.0 through 8.20.0 allows remote attackers controlling a WebSocket server to exhaust client memory. In lib/ws.c, automatic PONG handling queues each response into the WebSocket send buffer even when the server does not read acknowledgments, so sequential PING frames drive unbounded allocation. A target must initiate a WebSocket transfer to the malicious server with automatic PONG responses enabled; sustained flooding can return an out-of-memory error or starve the surrounding application.
The record
- CVE
- CVE-2026-11586
- Published
- Jul 3, 2026
- Updated
- Jul 3, 2026
- Vendor
- curl
- Product
- curl
- Classifications
- CWE-770, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 3, 2026CVE publishedPublication date reported by the CVE source.
- Jul 3, 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=8.16.0 <=8.16.0
- Affected versionversion=8.17.0 <=8.17.0
- Affected versionversion=8.18.0 <=8.18.0
- Affected versionversion=8.19.0 <=8.19.0
- Affected versionversion=8.20.0 <=8.20.0
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.
Weakness, pattern, technique
Public exploit references
- Upstream crazy PING regression testproof 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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