How severe is CVE-2026-5366?

CVE-2026-5366 has a CVSS 3.x base score of 9.9, rated critical 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 high.

Is CVE-2026-5366 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-5366?

CVE-2026-5366 affects Prefect. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-5366?

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

Does CVE-2026-5366 have an EU (EUVD) identifier?

Yes. CVE-2026-5366 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38128.

When was CVE-2026-5366 published?

CVE-2026-5366 was published on 2026-06-20 and last updated on 2026-07-01.

CVE-2026-5366

CVE-2026-5366 is a critical-severity vulnerability in Prefect with a CVSS 3.x base score of 9.9. 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-94.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
EPSS exploit prediction: 1% (55th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38128
Weakness: CWE-94
Affected product: Prefect
Published: 2026-06-20
Last modified: 2026-07-01

Description

Prefect version 3.6.23 is vulnerable to remote code execution due to improper handling of user-controlled input in the `GitRepository` storage class. The `commit_sha` parameter, which is passed to git commands, lacks validation and does not include a `--` separator to distinguish user input from git flags. This allows attackers to inject arbitrary git flags, such as `--upload-pack`, enabling execution of external programs. Additionally, the `directories` parameter can be exploited to inject git flags during sparse-checkout operations. These vulnerabilities allow any user with deployment creation permissions to execute arbitrary commands on worker machines, compromising shared work pools in multi-tenant environments.

Frequently asked questions

What is CVE-2026-5366?: Prefect version 3.6.23 is vulnerable to remote code execution due to improper handling of user-controlled input in the `GitRepository` storage class. The `commit_sha` parameter, which is passed to git commands, lacks validation and does not include a `--` separator to distinguish user input from git flags. This allows attackers to inject arbitrary git flags, such as `--upload-pack`, enabling execution of external programs. Additionally, the `directories` parameter can be exploited to inject git flags during sparse-checkout operations. These vulnerabilities allow any user with deployment creation permissions to execute arbitrary commands on worker machines, compromising shared work pools in multi-tenant environments.
How severe is CVE-2026-5366?: CVE-2026-5366 has a CVSS 3.x base score of 9.9, rated critical 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 high.
Is CVE-2026-5366 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-5366?: CVE-2026-5366 affects Prefect. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-5366?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-5366 have an EU (EUVD) identifier?: Yes. CVE-2026-5366 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38128.
When was CVE-2026-5366 published?: CVE-2026-5366 was published on 2026-06-20 and last updated on 2026-07-01.

References

https://huntr.com/bounties/e2e88a0f-a8f6-49c9-94c5-e98dc385f07a

Affected products (1)

cpe:2.3:a:prefect:prefect:3.6.23:-:*:*:*:*:*:*

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