Investigate in your agent.

Turn this advisory into a focused investigation. Ask your agent to check your project’s versions, explain the evidence, and suggest a compatible fix.

Your agent needs remote MCP support and access to https://cve.new/mcp.

Read the setup guide

Skip to content
cve.newCreate a CVE report
Check your stack
GO-2026-6603

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

Products / packages stdlib · golang.org/x/net

Published

Share

Severity and exploitation

Not in CISA KEVNo CVSS score

KEV coverage does not rule out exploitation.

KEV checked 14/11/2026, 23:35:33 UTC

Severity

unknown

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Package fixes recorded

Fix versions are recorded for 2 of 2 mapped packages. Check each release branch and any separate product guidance.

What this means

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…

Source excerpt · OSV

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

Packages

Compare each installed version with the publisher’s affected ranges. Where a fix is recorded, choose the appropriate release branch and test compatibility before upgrading.

stdlib Go
Affected range Recorded fix
Earlier releases before 1.26.9Semantic versions1.26.9
From 1.27.0-0 before 1.27.2Semantic versions1.27.2

Version evidence: OSV · GO-2026-6603

View original version evidence (0 explicit versions)
golang.org/x/net Go
Affected range Recorded fix
Earlier releases before 0.60.0Semantic versions0.60.0

Version evidence: OSV · GO-2026-6603

View original version evidence (0 explicit versions)

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

Use the recorded fix for your release branch. Review the publisher’s instructions and test compatibility before upgrading.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher description

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.

References

5 sources
go.dev/cl/847185
Source reference
go.dev/cl/847314
Source reference
go.dev/issue/81857
Source reference
groups.google.com/g/golang-announce/c/U2fTuyDJznI
Source reference
groups.google.com/g/golang-announce/c/ZPwCyRUuGBs
Source reference

Inside the record

Evidence available

Package identity
Version evidence
Remediation guidance · not supplied
Weakness classification · not supplied
Additional publishers · not supplied

Describes the evidence in this view, not whether the product is safe.

Original records

No official CVE record has been imported. Use the source links below for the original advisory.

cve.new JSON →

Timeline

All times UTC

  1. Advisory published

    Publication date supplied by the source.

  2. Source updated

    Latest modification date supplied by the source.

  3. Last imported by cve.new

    Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes
No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.