net/http: Multiple Operations on Resource in Single-Operation Context
CVE-2026-78663 is a critical-severity multiple operations on resource in single-operation context vulnerability in net/http from Go standard library, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 1.26.9 as the first without the flaw, so updating net/http to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.86% chance of exploitation within 30 days, higher than 59% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update net/http to 1.26.9 or a later version.
- Update net/http/internal/http2 to 1.27.2 or a later version.
- Update golang.org/x/net/http2 to 0.60.0 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Go standard library | net/http | before 1.26.9 | 1.26.9 |
| Go standard library | net/http/internal/http2 | 1.27.0-0 up to, but not including, 1.27.2 | 1.27.2 |
| Golang.org/x/net | golang.org/x/net/http2 | before 0.60.0 | 0.60.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H. Scored by CISA (ADP).
Official description
The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Multiple Operations on Resource in Single-Operation Context
The product performs the same operation on a resource two or more times, when the operation should only be applied once.
More Multiple Operations on Resource in Single-Operation Context vulnerabilities (CWE-675)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in net/http
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent Multiple Operations on Resource in Single-Operation Context vulnerabilities
- 8.4 High severity
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