CVE-2026-34040 is a high-severity (CVSS 8.8) CWE-288 vulnerability in github.com/moby/moby. A fix is available for github.com/moby/moby — see the affected versions and patch details below.
Moby: AuthZ plugin bypass with oversized request body
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34040.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-34040 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/moby/moby🐹github.com/moby/moby/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
A security vulnerability has been detected that allows attackers to bypass authorization plugins (AuthZ) under specific circumstances. The base likelihood of this being exploited is low.
This is an incomplete fix for CVE-2024-41110.
Impact
If you don't use AuthZ plugins, you are not affected.
Using a specially-crafted API request, an attacker could make the Docker daemon forward the request to an authorization plugin without the body. The authorization plugin may allow a request which it would have otherwise denied if the body had been forwarded to it.
Anyone who depends on authorization plugins that introspect the request body to make access control decisions is potentially impacted.
Workarounds
If unable to update immediately:
- Avoid using AuthZ plugins that rely on request body inspection for security decisions.
- Restrict access to the Docker API to trusted parties, following the principle of least privilege.
Credits
- 1seal / Oleh Konko (@1seal)
- Cody ([email protected])
- Asim Viladi Oglu Manizada (@manizada)
Resources
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/moby/moby | all versions | 29.3.1go get github.com/moby/moby@v29.3.1 |
| 🐹Go | github.com/moby/moby/v2 | all versions | 2.0.0-beta.8go get github.com/moby/moby/v2@v2.0.0-beta.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/moby/moby, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/moby/moby to 29.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34040 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-34040 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-34040. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Multicluster Global Hub 1.4.9 | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1779579439 | RHSA-2026:22347 |
| Multicluster Global Hub 1.4.9 | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1788375682 | RHSA-2026:67516 |
| Multicluster Global Hub 1.6.5 | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1780167118 | RHSA-2026:23345 |
| Multicluster Global Hub 1.7.3 | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1779925273 | RHSA-2026:24503 |
| Multicluster Global Hub 1.7.3 | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1788376193 | RHSA-2026:67842 |
| Red Hat multicluster global hub 1.5.3 | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1778867753 | RHSA-2026:21769 |
Frequently Asked Questions
Is CVE-2026-34040 in your dependencies?
O3 Security finds CVE-2026-34040 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.