Service exhaustion via unbounded HPACK table growth
Published Sep 18, 2026 · Updated Sep 18, 2026
Resource exhaustion in Netty's HTTP/2 HpackEncoder allows remote attackers to interrupt services through crafted SETTINGS frames. DefaultHttp2HeadersEncoder passes a peer-controlled MAX_HEADER_TABLE_SIZE directly to HpackEncoder, which retains unique response headers and performs O(n²) chain scans as the table grows. An unauthenticated HTTP/2 client must keep a connection active and elicit changing response headers; CPU and memory pressure can reduce request throughput to near zero.
Summary
What happened
Resource exhaustion in Netty's HTTP/2 HpackEncoder allows remote attackers to interrupt services through crafted SETTINGS frames. DefaultHttp2HeadersEncoder passes a peer-controlled MAX_HEADER_TABLE_SIZE directly to HpackEncoder, which retains unique response headers and performs O(n²) chain scans as the table grows. An unauthenticated HTTP/2 client must keep a connection active and elicit changing response headers; CPU and memory pressure can reduce request throughput to near zero.
The record
- CVE
- CVE-2026-93492
- Published
- Sep 18, 2026
- Updated
- Sep 18, 2026
- Vendor
- Commonhaus Foundation
- Product
- Red Hat AMQ Broker 7
- Classifications
- CWE-1035, T1499.003
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 18, 2026CVE publishedPublication date reported by the CVE source.
- Sep 18, 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?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
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
- Netty HTTP/2 HpackEncoder resource-exhaustion PoCproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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