CVE-2026-786597.5HighCWE-405

CVE-2026-78659: HTTP/2 server memory exhaustion due to Trailer headers in net/http

Go standard library · net/http

Vendor fix available · Affected: Go standard library net/http · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.9%probability of exploitation in the next 30 days

59th percentile

050100

Higher than 59% of scored CVEs

7.5HighCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products3

From the CVE record. A product or version that is not listed is unknown, not unaffected.

Go standard library · net/httpbefore 1.26.9
Go standard library · net/http/internal/http2from 1.27.0-0 before 1.27.2
golang.org/x/net · golang.org/x/net/http2before 0.60.0

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Asymmetric Resource Consumption (Amplification) · Denial of Service
Vendor: Go standard library
Published: October 2026
Band: Unlikely (under 1%), October 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-78659 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.