Cross-client response disclosure via processor recycling race
Published Sep 28, 2022 · Updated May 21, 2025
Race condition in affected Apache Tomcat releases allows remote attackers to receive another client's HTTP response or response fragment. AbstractProtocol's connection handler reads and clears a SocketWrapper's current Processor non-atomically, allowing concurrent threads to release and reuse one Http11Processor for two client connections. The rare race affects 8.5.0 through 8.5.77, 9.0.0-M1 through 9.0.60, 10.0.0-M1 through 10.0.18, and 10.1.0-M1 through 10.1.0-M12; disclosure is limited to misdirected response data.
Summary
What happened
Race condition in affected Apache Tomcat releases allows remote attackers to receive another client's HTTP response or response fragment. AbstractProtocol's connection handler reads and clears a SocketWrapper's current Processor non-atomically, allowing concurrent threads to release and reuse one Http11Processor for two client connections. The rare race affects 8.5.0 through 8.5.77, 9.0.0-M1 through 9.0.60, 10.0.0-M1 through 10.0.18, and 10.1.0-M1 through 10.1.0-M12; disclosure is limited to misdirected response data.
The record
- CVE
- CVE-2021-43980
- Published
- Sep 28, 2022
- Updated
- May 21, 2025
- Vendor
- The Apache Software Foundation
- Product
- Apache Tomcat
- Classifications
- CWE-362, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 28, 2022CVE publishedPublication date reported by the CVE source.
- May 21, 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=10.0.0-M1 to 10.0.18
- Affected versionversion=10.1.0-M1 to 10.1.0-M12
- Affected versionversion=8.5.0 to 8.5.77
- Affected versionversion=9.0.0-M1 to 9.0.60
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
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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