How severe is CVE-2025-21355?

CVE-2025-21355 has a CVSS 3.x base score of 8.6, 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-2025-21355 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-21355?

CVE-2025-21355 affects Microsoft Bing. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-21355?

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-2025-21355 have an EU (EUVD) identifier?

Yes. CVE-2025-21355 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-4643.

When was CVE-2025-21355 published?

CVE-2025-21355 was published on 2025-02-19 and last updated on 2026-06-17.

CVE-2025-21355

CVE-2025-21355 is a high-severity vulnerability in Microsoft Bing with a CVSS 3.x base score of 8.6. 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-306.

Key facts

Severity: High (CVSS 3.x base score 8.6)
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-4643
Weakness: CWE-306
Affected product: Microsoft Bing
Published: 2025-02-19
Last modified: 2026-06-17

Description

Missing Authentication for Critical Function in Microsoft Bing allows an unauthorized attacker to execute code over a network

Frequently asked questions

What is CVE-2025-21355?: Missing Authentication for Critical Function in Microsoft Bing allows an unauthorized attacker to execute code over a network
How severe is CVE-2025-21355?: CVE-2025-21355 has a CVSS 3.x base score of 8.6, 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-2025-21355 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21355?: CVE-2025-21355 affects Microsoft Bing. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-21355?: 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-2025-21355 have an EU (EUVD) identifier?: Yes. CVE-2025-21355 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-4643.
When was CVE-2025-21355 published?: CVE-2025-21355 was published on 2025-02-19 and last updated on 2026-06-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21355

Affected products (1)

cpe:2.3:a:microsoft:bing:*:*:*:*:*:*:*:*

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