How severe is CVE-2025-21620?

CVE-2025-21620 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2025-21620 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2025-21620?

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-2025-21620 have an EU (EUVD) identifier?

Yes. CVE-2025-21620 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-0024.

When was CVE-2025-21620 published?

CVE-2025-21620 was published on 2025-01-06 and last updated on 2026-06-17.

CVE-2025-21620

CVE-2025-21620 is a high-severity vulnerability with a CVSS 3.x base score of 7.5. 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-200.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-0024
Weakness: CWE-200
Published: 2025-01-06
Last modified: 2026-06-17

Description

Deno is a JavaScript, TypeScript, and WebAssembly runtime with secure defaults. When you send a request with the Authorization header to one domain, and the response asks to redirect to a different domain, Deno'sfetch() redirect handling creates a follow-up redirect request that keeps the original Authorization header, leaking its content to that second domain. This vulnerability is fixed in 2.1.2.

Frequently asked questions

What is CVE-2025-21620?: Deno is a JavaScript, TypeScript, and WebAssembly runtime with secure defaults. When you send a request with the Authorization header to one domain, and the response asks to redirect to a different domain, Deno'sfetch() redirect handling creates a follow-up redirect request that keeps the original Authorization header, leaking its content to that second domain. This vulnerability is fixed in 2.1.2.
How severe is CVE-2025-21620?: CVE-2025-21620 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2025-21620 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2025-21620?: 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-2025-21620 have an EU (EUVD) identifier?: Yes. CVE-2025-21620 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-0024.
When was CVE-2025-21620 published?: CVE-2025-21620 was published on 2025-01-06 and last updated on 2026-06-17.

References

https://github.com/denoland/deno/security/advisories/GHSA-f27p-cmv8-xhm6

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