Client denial of service via unbounded response headers
Published Sep 15, 2023 · Updated Dec 2, 2025
Denial of service in curl 7.84.0 through 8.2.1 allows remote attackers controlling an HTTP server to exhaust client heap memory. libcurl's headers API stores each received response header in a separate heap allocation without limiting their aggregate size or count. The client must request content from the attacker-controlled server; sustained header delivery consumes memory until the invoking process or host service is interrupted.
Summary
What happened
Denial of service in curl 7.84.0 through 8.2.1 allows remote attackers controlling an HTTP server to exhaust client heap memory. libcurl's headers API stores each received response header in a separate heap allocation without limiting their aggregate size or count. The client must request content from the attacker-controlled server; sustained header delivery consumes memory until the invoking process or host service is interrupted.
The record
- CVE
- CVE-2023-38039
- Published
- Sep 15, 2023
- Updated
- Dec 2, 2025
- Vendor
- curl
- Product
- curl
- Classifications
- CWE-770, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 15, 2023CVE publishedPublication date reported by the CVE source.
- Dec 2, 2025Record 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=8.3.0 <8.3.0
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
- HackerOne report 2072338 proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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