cmd/go: Incorrect Authorization
CVE-2026-27140 is a high-severity incorrect authorization vulnerability in cmd/go from Go toolchain, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions 1.25.9, 1.26.2 as the first without the flaw, so updating cmd/go to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.67% chance of exploitation within 30 days, higher than 53% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update cmd/go to 1.25.9 or 1.26.2, whichever matches your release line, or a later version.
- Update Go to 1.25.9 or 1.26.2, whichever matches your release line, or a later version.
- Read the advisory on pkg.go.dev for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
Version data comes from the organisation that assigned the CVE; 2 further products are omitted here. 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
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- 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:R/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 3.1 | 8.8 | High | CISA (ADP) |
| CVSS 3.1 | 9.0 | Critical | CNA |
Official description
SWIG file names containing 'cgo' and well-crafted payloads could lead to code smuggling and arbitrary code execution at build time due to trust layer bypass.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incorrect Authorization
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
How developers prevent this class of flaw
- Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework and the OWASP ESAPI Access Control feature.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
- go.dev/cl/763768Release Notes
- groups.google.com/g/golang-announce/c/0uYbvbPZRWUMailing List, Release Notes
Other references
- go.dev/issue/78335Issue Tracking
- access.redhat.com/errata/RHSA-2026:10217
- access.redhat.com/errata/RHSA-2026:10219
- access.redhat.com/errata/RHSA-2026:10704
- access.redhat.com/errata/RHSA-2026:16021
- access.redhat.com/errata/RHSA-2026:16024
- access.redhat.com/errata/RHSA-2026:16494
- access.redhat.com/errata/RHSA-2026:16497
- access.redhat.com/errata/RHSA-2026:16498
- access.redhat.com/errata/RHSA-2026:16694
- access.redhat.com/errata/RHSA-2026:16697
- access.redhat.com/errata/RHSA-2026:16698
- access.redhat.com/errata/RHSA-2026:23246
- access.redhat.com/errata/RHSA-2026:25182
- access.redhat.com/errata/RHSA-2026:34099
Other vulnerabilities in cmd/go
- 7.8 High severity
- 7.8 High severity
- 8.4 High severity
- 7.5 High severity
- 7.5 High severity
- 7.0 High severity
Recent Incorrect Authorization vulnerabilities
- 7.1 High severity
- 8.1 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 8.1 High severity
- 8.8 High severity
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