GO-2026-6603 BIT-golang-2026-78659 CVE-2026-78659
HTTP/2 server memory exhaustion due to Trailer headers in net/http
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.63%
- Chance of exploitation in the next 30 days. Higher than 50.09% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-405 Asymmetric Resource Consumption (Amplification)
- Fix
- Available
- 2 packages have a fixed version
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.
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| golang.org/x/net | < 0.60.0 |
0.60.0 |
| stdlib | < 1.26.9 |
1.26.9 |
| stdlib | >= 1.27.0-0, < 1.27.2 |
1.27.2 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
golang.org/x/net Go → 0.60.0
- go
go get golang.org/x/net@v0.60.0 && go mod tidy
stdlib Go → 1.26.9
- go
go get stdlib@v1.26.9 && go mod tidy
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-405: Asymmetric Resource Consumption (Amplification)
The product does not properly control situations in which an adversary can cause the product to consume or produce excessive resources without requiring the adversary to invest equivalent work or otherwise prove authorization, i.e., the adversary's influence is "asymmetric."
How to prevent it
- Architecture and Design: An application must make resources available to a client commensurate with the client's access level.
- Architecture and Design: An application must, at all times, keep track of allocated resources and meter their usage appropriately.
- System Configuration: Consider disabling resource-intensive algorithms on the server side, such as Diffie-Hellman key exchange.
References
Fixes and patches
Issue reports
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-4374-p667-p6c8 HTTP/2 rapid reset can cause excessive work in net/http | High Known exploited | Also affects golang.org/x/net |
| GHSA-qppj-fm5r-hxr3 HTTP/2 Stream Cancellation Attack | Medium Known exploited | Also affects golang.org/x/net |
| CVE-2020-0601 Certificate validation bypass on Windows in crypto/x509 | High Known exploited | Also affects stdlib |
| GO-2026-6866 Check all ancestor namespace transitions when rendering raw text in html in golang.org/x/net | Not rated yet | Also affects golang.org/x/net |
| GO-2026-6860 Avoid quadratic complexity when coalescing text nodes in html in golang.org/x/net | Not rated yet | Also affects golang.org/x/net |
| RUSTSEC-2026-0382 Distrust compromised intermediate certificates in crypto/x509 | Medium | Also affects stdlib |
| GO-2026-6613 HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http | High | Also affects stdlib |
| GO-2026-6609 Lack of limit on size of parsed Range headers in net/http | High | Also affects stdlib |
Credits: RyotaK (https://ryotak.net) of GMO Flatt Security Inc.
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