How severe is CVE-2026-40937?

CVE-2026-40937 has a CVSS 3.x base score of 8.3, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.

Is CVE-2026-40937 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40937?

CVE-2026-40937 primarily affects Rustfs. In total, 93 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-40937?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-40937 have an EU (EUVD) identifier?

Yes. CVE-2026-40937 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25092.

When was CVE-2026-40937 published?

CVE-2026-40937 was published on 2026-04-22 and last updated on 2026-06-17.

CVE-2026-40937

CVE-2026-40937 is a high-severity vulnerability in Rustfs with a CVSS 3.x base score of 8.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-862.

Key facts

Severity: High (CVSS 3.x base score 8.3)
EPSS exploit prediction: 0% (21st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-25092
Weakness: CWE-862
Affected product: Rustfs
Published: 2026-04-22
Last modified: 2026-06-17

Description

RustFS is a distributed object storage system built in Rust. Prior to 1.0.0-alpha.94, all four notification target admin API endpoints in `rustfs/src/admin/handlers/event.rs` use a `check_permissions` helper that validates authentication only (access key + session token), without performing any admin-action authorization via `validate_admin_request`. Every other admin handler in the codebase correctly calls `validate_admin_request` with a specific `AdminAction`. This is the only admin handler file that skips authorization. A non-admin user can overwrite a shared admin-defined notification target by name, causing subsequent bucket events to be delivered to an attacker-controlled endpoint. This enables cross-user event interception and audit evasion. 1.0.0-alpha.94 contains a patch.

Frequently asked questions

What is CVE-2026-40937?: RustFS is a distributed object storage system built in Rust. Prior to 1.0.0-alpha.94, all four notification target admin API endpoints in `rustfs/src/admin/handlers/event.rs` use a `check_permissions` helper that validates authentication only (access key + session token), without performing any admin-action authorization via `validate_admin_request`. Every other admin handler in the codebase correctly calls `validate_admin_request` with a specific `AdminAction`. This is the only admin handler file that skips authorization. A non-admin user can overwrite a shared admin-defined notification target by name, causing subsequent bucket events to be delivered to an attacker-controlled endpoint. This enables cross-user event interception and audit evasion. 1.0.0-alpha.94 contains a patch.
How severe is CVE-2026-40937?: CVE-2026-40937 has a CVSS 3.x base score of 8.3, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.
Is CVE-2026-40937 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40937?: CVE-2026-40937 primarily affects Rustfs. In total, 93 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-40937?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-40937 have an EU (EUVD) identifier?: Yes. CVE-2026-40937 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25092.
When was CVE-2026-40937 published?: CVE-2026-40937 was published on 2026-04-22 and last updated on 2026-06-17.

References

Affected products (93)

cpe:2.3:a:rustfs:rustfs:1.0.0:alpha1:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha10:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha11:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha12:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha13:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha14:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha15:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha16:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha17:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha18:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha19:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha2:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha20:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha21:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha22:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha23:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha24:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha25:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha26:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha27:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha28:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha29:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha3:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha30:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha31:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha32:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha33:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha34:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha35:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha36:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha37:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha38:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha39:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha4:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha40:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha41:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha42:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha43:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha44:*:*:*:rust:*:*
cpe:2.3:a:rustfs:rustfs:1.0.0:alpha45:*:*:*:rust:*:*

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