CVE-2026-42501
published 2026-05-07CVE-2026-42501: A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability…
PriorityP346high7.5CVSS 3.1
AVNACHPRNUIRSUCHIHAH
EPSS
0.23%
13.8th percentile
A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain. Since this vulnerability affects the security of toolchain downloads, setting GOTOOLCHAIN to a fixed version is not sufficient. You must upgrade your base Go toolchain. The go tool always validates the hash of a toolchain before executing it, so fixed versions will refuse to execute any cached, altered versions of the toolchain. The go tool trusts go.sum files to contain accurate hashes of the current module's dependencies. A malicious proxy exploiting this vulnerability to serve an altered module will have caused an incorrect hash to be recorded in the go.sum. Users who have configured a non-trusted GOPROXY can determine if they have been affected by running "rm go.sum ; go mod tidy ; go mod verify", which will revalidate all dependencies of the current module. The specific flaw in more detail: The go command consults the checksum database to validate downloaded modules, when a module is not listed in the go.sum file. It verifies that the module hash reported by the checksum database matches the hash of the downloaded module. If, however, the checksum database returns a successful response that contains no entry for the module, the go command incorrectly permitted validation to succeed. A module proxy may mirror or proxy the checksum database, in which case the go command will not connect to
Affected
25 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| exploit-intelligence-tech-preview | vulnerability-analysis-rhel9 | — | — |
| go-toolset_rhel8 | golang | — | — |
| go_toolchain | cmd_go | < 1.25.10 | 1.25.10 |
| go_toolchain | cmd_go | >= 1.26.0-0 < 1.26.3 | 1.26.3 |
| golang | go | < 1.25.10 | 1.25.10 |
| golang | go | >= 1.26.0 < 1.26.3 | 1.26.3 |
| multicluster-engine | addon-manager-rhel9 | — | — |
| multicluster-engine | backplane-rhel9-operator | — | — |
| multicluster-engine | clusterlifecycle-state-metrics-rhel9 | — | — |
| multicluster-engine | hypershift-addon-rhel9-operator | — | — |
| multicluster-engine | maestro-rhel9 | — | — |
| multicluster-engine | managedcluster-import-controller-rhel9 | — | — |
| multicluster-engine | multicloud-manager-rhel9 | — | — |
| multicluster-engine | placement-rhel9 | — | — |
| multicluster-engine | registration-operator-rhel9 | — | — |
| multicluster-engine | registration-rhel9 | — | — |
| multicluster-engine | work-rhel9 | — | — |
| oadp | oadp-velero-rhel9 | — | — |
| openshift4 | ose-hypershift-rhel9 | — | — |
| rh-osbs | openshift-golang-builder | — | — |
| rhacm2 | acm-governance-policy-addon-controller-rhel9 | — | — |
| rhacm2 | acm-governance-policy-framework-addon-rhel9 | — | — |
| rhacm2 | config-policy-controller-rhel9 | — | — |
| rhacm2 | governance-policy-propagator-rhel9 | — | — |
| rhacm2 | klusterlet-addon-controller-rhel9 | — | — |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
vendor_redhat7.5HIGH
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VulDB
cmd-go up to 1.25.9/1.26.2 on Go signature verification (EUVD-2026-28433)
vuldb·2026-05-07
CVE-2026-42501 [LOW] cmd-go up to 1.25.9/1.26.2 on Go signature verification (EUVD-2026-28433)
A vulnerability was found in cmd-go up to 1.25.9/1.26.2 on Go. It has been rated as problematic. Impacted is an unknown function. The manipulation leads to improper verification of cryptographic signature.
This vulnerability is traded as CVE-2026-42501. It is possible to initiate the attack remotely. There is no exploit available.
Upgrading the affected component is advised.
GHSA
GHSA-qf3q-3h68-mmh2: A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation
ghsa_unreviewed·2026-05-07
CVE-2026-42501 [HIGH] CWE-347 GHSA-qf3q-3h68-mmh2: A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation
A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain. Since this vulnerability affects the security of toolchain downloads, setting GOTOOLCHAIN to a fixed version is n
Red Hat
cmd/go: golang: Go command (cmd/go): Integrity bypass due to checksum validation flaw via malicious module proxy
vendor_redhat·2026-05-07·CVSS 7.5
CVE-2026-42501 [HIGH] CWE-347 cmd/go: golang: Go command (cmd/go): Integrity bypass due to checksum validation flaw via malicious module proxy
cmd/go: golang: Go command (cmd/go): Integrity bypass due to checksum validation flaw via malicious module proxy
A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain.
No detection rules found.
No public exploits indexed.
Rapid7
Patch Tuesday - May 2026
blogs_rapid7·2026-05-13·CVSS 10.0
CVE-2026-41089 [CRITICAL] Patch Tuesday - May 2026
Microsoft is publishing 137 vulnerabilities on May 2026 Patch Tuesday . Microsoft is not aware of exploitation in the wild or public disclosure for any of these vulnerabilities. So far this month, Microsoft has provided patches to address 133 browser vulnerabilities, which are not included in the Patch Tuesday count above.
## Windows Netlogon: critical RCE
Anyone responsible for securing a domain controller should prioritize remediation of CVE-2026-41089 , which is a critical stack-based buffer overflow in Windows Netlogon with a CVSS v3 base score of 9.8. Exploitation leads to execution in the context of the Netlogon service, so that’s SYSTEM privileges on the domain controller. For most pentesters, that’s the point at which the customer report more or less writes itself. No privileges
Bugzilla
CVE-2026-42501 cmd/go: golang: Go command (cmd/go): Integrity bypass due to checksum validation flaw via malicious module proxy
bugzilla·2026-05-07·CVSS 7.5
CVE-2026-42501 [HIGH] CVE-2026-42501 cmd/go: golang: Go command (cmd/go): Integrity bypass due to checksum validation flaw via malicious module proxy
CVE-2026-42501 cmd/go: golang: Go command (cmd/go): Integrity bypass due to checksum validation flaw via malicious module proxy
A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downlo
2026-05-07
Published