How severe is CVE-2026-45503?

CVE-2026-45503 has a CVSS 3.x base score of 8.1, 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 none.

Is CVE-2026-45503 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-45503?

CVE-2026-45503 primarily affects Microsoft Exchange Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-45503?

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-2026-45503 have an EU (EUVD) identifier?

Yes. CVE-2026-45503 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35679.

When was CVE-2026-45503 published?

CVE-2026-45503 was published on 2026-06-09 and last updated on 2026-06-17.

CVE-2026-45503

CVE-2026-45503 is a high-severity vulnerability in Microsoft Exchange Server with a CVSS 3.x base score of 8.1. 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-918.

Key facts

Severity: High (CVSS 3.x base score 8.1)
EPSS exploit prediction: 0% (36th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-35679
Weakness: CWE-918
Affected product: Microsoft Exchange Server
Published: 2026-06-09
Last modified: 2026-06-17

Description

Server-side request forgery (ssrf) in Microsoft Exchange Server allows an authorized attacker to disclose information over a network.

Frequently asked questions

What is CVE-2026-45503?: Server-side request forgery (ssrf) in Microsoft Exchange Server allows an authorized attacker to disclose information over a network.
How severe is CVE-2026-45503?: CVE-2026-45503 has a CVSS 3.x base score of 8.1, 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 none.
Is CVE-2026-45503 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-45503?: CVE-2026-45503 primarily affects Microsoft Exchange Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-45503?: 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-2026-45503 have an EU (EUVD) identifier?: Yes. CVE-2026-45503 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35679.
When was CVE-2026-45503 published?: CVE-2026-45503 was published on 2026-06-09 and last updated on 2026-06-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45503

Affected products (4)

cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_23:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_14:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_15:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server_subscription_edition:*:*:*:*:*:*:*:*

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