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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://go.dev/cl/847185
https://go.dev/cl/847314
https://go.dev/issue/81857
https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs
https://pkg.go.dev/vuln/GO-2026-6603

Configurations

No configuration.

History

09 Oct 2026, 16:17

Type	Values Removed	Values Added
CWE		CWE-405
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5

08 Oct 2026, 23:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-08 23:17

Updated : 2026-10-09 16:35

NVD link : CVE-2026-78659

Mitre link : CVE-2026-78659

CVE.ORG link : CVE-2026-78659

JSON object : View

Products Affected

No product.

CWE

CWE-405

Asymmetric Resource Consumption (Amplification)

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"https://pkg.go.dev/vuln/GO-2026-6603", "source": "security@golang.org"}], "vulnStatus": "Awaiting Analysis", "weaknesses": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "description": [{"lang": "en", "value": "CWE-405"}]}], "descriptions": [{"lang": "en", "value": "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."}], "lastModified": "2026-10-09T16:35:35.900", "sourceIdentifier": "security@golang.org"}