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 3.1
- 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS
- 0.6% chance of exploitation in the next 30 days; higher than 49% of CVEs (scores of 2026-10-25)
- CWE
- CWE-405
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GO-2026-6603 | Go | stdlib | <1.26.9 | 1.26.9 |
| GO-2026-6603 | Go | stdlib | >=1.27.0-0 <1.27.2 | 1.27.2 |
| GO-2026-6603 | Go | golang.org/x/net | <0.60.0 | 0.60.0 |