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Vulnerabilities

Vulnerability · CVE-2026-78659

HTTP/2 server memory exhaustion due to Trailer headers in net/http

Published Oct 8, 2026 · catalog updated Oct 16, 2026 · HTTP/2 server memory exhaustion

Check if you run it

No confirmed exploitation is on record for CVE-2026-78659. EPSS is 0.57%. Act only if a listed version of HTTP/2 server memory exhaustion is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (HTTP/2 server memory exhaustion).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.57%
Remediation
Not established
Affected products
Go golang.org/x/net · Go stdlib

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Go golang.org/x/net0 → 0.60.0
  • Go stdlib0 → 1.26.9
  • Go stdlib1.27.0-0 → 1.27.2

How to fix CVE-2026-78659

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-78659. EPSS is 0.57%. Act only if a listed version of HTTP/2 server memory exhaustion is installed.

Which versions are affected?

Compare what you have installed with 0 → 0.60.0, 0 → 1.26.9, 1.27.0-0 → 1.27.2. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.57%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 8, 2026 · OpenSSF OSV / OSV Scanner

    Detected

    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 disproporti

  2. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    stdlib fixed in 1.26.9; stdlib fixed in 1.27.2; golang.org/x/net fixed in 0.60.0

  3. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    stdlib fixed in 1.26.9

  4. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    stdlib fixed in 1.27.2

  5. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    golang.org/x/net fixed in 0.60.0

  6. Oct 16, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    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 disproporti

Sources

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.