Microsoft Exchange Server vulnerabilities: known CVEs & security history
Microsoft · Microsoft · 48 tracked CVEs · 11 actively exploited · updated September 2026 · what is a CVE? →
This is the full list of known vulnerabilities (CVEs) across all Microsoft Exchange Server release lines — 48 in total, with 11 actively exploited in the wild. A CVE here doesn't mean your version is affected — check Microsoft Exchange Server's current status and the safe version to run.
Known Microsoft Exchange Server CVEs
Actively-exploited and most-severe first. Open any CVE for full details.
| CVE | Severity | CVSS | EPSS | Year |
|---|---|---|---|---|
| CVE-2021-34473⚡ exploited | critical | 9.1 | 100% | 2021 |
| CVE-2021-26855⚡ exploited | critical | 9.1 | 100% | 2021 |
| CVE-2021-34523⚡ exploited | critical | 9 | 100% | 2021 |
| CVE-2023-21529⚡ exploited | high | 8.8 | 62% | 2023 |
| CVE-2022-41080⚡ exploited | high | 8.8 | 77% | 2022 |
| CVE-2021-42321⚡ exploited | high | 8.8 | 90% | 2021 |
| CVE-2021-27065⚡ exploited | high | 7.8 | 100% | 2021 |
| CVE-2021-26858⚡ exploited | high | 7.8 | 90% | 2021 |
| CVE-2021-26857⚡ exploited | high | 7.8 | 94% | 2021 |
| CVE-2021-33766⚡ exploited | high | 7.3 | 98% | 2021 |
| CVE-2021-31196⚡ exploited | high | 7.2 | 46% | 2021 |
| CVE-2023-21709 | critical | 9.8 | 2% | 2023 |
| CVE-2026-55008 | critical | 9.6 | 1% | 2026 |
| CVE-2021-27078 | critical | 9.1 | 18% | 2021 |
| CVE-2021-26412 | critical | 9.1 | 30% | 2021 |
| CVE-2026-62913 | high | 8.8 | 1% | 2026 |
| CVE-2026-55005 | high | 8.8 | 1% | 2026 |
| CVE-2026-45504 | high | 8.8 | 1% | 2026 |
| CVE-2023-38185 | high | 8.8 | 3% | 2023 |
| CVE-2023-38181 | high | 8.8 | 11% | 2023 |
| CVE-2023-35368 | high | 8.8 | 2% | 2023 |
| CVE-2023-21707 | high | 8.8 | 82% | 2023 |
| CVE-2023-21706 | high | 8.8 | 4% | 2023 |
| CVE-2026-47631 | high | 8.1 | 0% | 2026 |
| CVE-2026-45503 | high | 8.1 | 0% | 2026 |
| CVE-2026-62911 | high | 8 | 1% | 2026 |
| CVE-2023-38182 | high | 8 | 6% | 2023 |
| CVE-2023-35388 | high | 8 | 7% | 2023 |
| CVE-2022-41079 | high | 8 | 1% | 2022 |
| CVE-2022-41078 | high | 8 | 1% | 2022 |
| CVE-2021-34470 | high | 8 | 3% | 2021 |
| CVE-2021-33768 | high | 8 | 1% | 2021 |
| CVE-2026-55009 | high | 7.8 | 2% | 2026 |
| CVE-2026-55006 | high | 7.8 | 0% | 2026 |
| CVE-2022-41123 | high | 7.8 | 1% | 2022 |
| CVE-2021-31206 | high | 7.6 | 10% | 2021 |
| CVE-2026-45583 | high | 7.5 | 0% | 2026 |
| CVE-2026-62914 | high | 7.3 | 1% | 2026 |
| CVE-2026-62910 | high | 7.2 | 1% | 2026 |
| CVE-2021-26854 | medium | 6.6 | 20% | 2021 |
| CVE-2026-65813 | medium | 6.5 | 1% | 2026 |
| CVE-2026-62915 | medium | 6.5 | 0% | 2026 |
| CVE-2026-62912 | medium | 6.5 | 1% | 2026 |
| CVE-2026-45501 | medium | 6.5 | 0% | 2026 |
| CVE-2021-42305 | medium | 6.5 | 8% | 2021 |
| CVE-2021-41349 | medium | 6.5 | 94% | 2021 |
| CVE-2026-45500 | medium | 6.1 | 0% | 2026 |
| CVE-2026-45502 | medium | 5 | 20% | 2026 |
Is my Microsoft Exchange Server version affected?
The list above spans every release. To know whether your version is affected — and the minimum safe version to upgrade to — check it directly.
Check your Microsoft Exchange Server version → · Monitor Microsoft Exchange Server for new CVEs →
Microsoft Exchange Server vulnerabilities — frequently asked
How many known vulnerabilities does Microsoft Exchange Server have?
IsItPatched tracks 48 CVEs for Microsoft Exchange Server, 11 of which are actively exploited (CISA KEV). 7 are critical-severity and 32 high-severity. These span every release line — what matters is whether the version you run is affected.
Does Microsoft Exchange Server have any actively-exploited vulnerabilities?
Yes — 11 Microsoft Exchange Server CVEs are in CISA's Known Exploited Vulnerabilities catalog, meaning they are confirmed exploited in the wild (9 linked to ransomware). Patch these as a priority.
What is the most severe Microsoft Exchange Server vulnerability?
Among tracked issues, CVE-2021-34473 (CRITICAL, CVSS 9.1), which is actively exploited, ranks highest — a Server-side request forgery (SSRF) weakness.
Is Microsoft Exchange Server safe to use?
It depends on the version. The latest supported Microsoft Exchange Server release (15.2.2562.46) clears the known issues; older versions may still be affected. Check the exact version you run for a verdict.
CVE data aggregated from NVD, CISA KEV and EPSS (FIRST.org). Related: Microsoft Exchange Server security status · Microsoft Exchange Server end-of-life · actively-exploited CVEs. Always verify against Microsoft's advisories — see our disclaimer.