Vulnerability Intelligence Report
HTTP/2 server memory exhaustion due to Trailer headers in net/http
CVE-2026-78659
When "Trailer" headers are sent by a client, the HTTP server internally uses the header values to populate the Request.Trailer map passed to the server handler. Because Request.Trailer is a map, each entry incurs memory overhead. For HTTP/2 servers, a malicious client can exploit this by sending a "Trailer" header that declares a large number of fields, causing the server to allocate a disproportionate amount of memory while bypassing Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits. This exploit is not applicable for HTTP/1 servers, which do not support multiplexing a large number of requests over one TCP connection, and whose Server.MaxHeaderBytes are calculated differently.
No Active Exploit Signals
CVSS Base Score
7.5
HIGH
Exploitability:3.9
Impact Score:3.6
EPSS Probability:0.23%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
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Authentication
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Weaponization
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SSVC Action
—
Weaknesses (CWE)
CWE-405 ↗CWE-405: Asymmetric Resource Consumption (Amplification)
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Go standard library | net/http | 0 < 1.26.9 (affected) |
| Go standard library | net/http/internal/http2 | 1.27.0-0 < 1.27.2 (affected) |
| golang.org/x/net | golang.org/x/net/http2 | 0 < 0.60.0 (affected) |
Threat Intelligence Signals
EPSS Score
0.227%
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Go Project · Vendor · USA |
| Reserved | 2026-08-24T23:36:03 |
| Published | 2026-10-08T22:53:58 |
| Last Updated | 2026-10-09T15:34:24 |
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