Security CISA KEV CVE-2021-26857 CVE-2021-26857 CISA KEV
Microsoft Exchange Server Remote Code Execution Vulnerability
Severity unknown CVSS unknown Check the vendor advisory for fixed versions
CISA lists this Microsoft vulnerability as known exploited. Its MSRC release detail is outside this installation's collected history.
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
Product Exchange Server
Added to KEV 3 Nov 2021
Federal remediation due 3 May 2022
Known ransomware use Yes
Changes are dated when recorded; day views use the last saved version from that UTC day, and citations stay fixed.
Cite this version Field-level log (2)
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23 Oct 2026 · 09:33:49 UTC
Source coverage: cisa-kev Incomplete → Current 23 Oct 2026 · 08:31:50 UTC
Source coverage: cisa-kev Current → Incomplete Explore global source statements, affected packages and advisory history for CVE-2021-26857 . The catalog has a separate collection scope from Microsoft release records.
More advisories, affected versions and source history
cve-program · CVE-2021-26857 Published Microsoft Exchange Server 2010 Service Pack 3 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2010 Service Pack 3",
"versions": [
{
"version": "14.0.0.0",
"lessThan": "14.03.0513.000",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2013 Cumulative Update 21 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2013 Cumulative Update 21",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.00.0",
"lessThan": "15.00.1395.012",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2013 Cumulative Update 22 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2013 Cumulative Update 22",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.00.0",
"lessThan": "15.00.1473.006",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2013 Cumulative Update 23 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2013 Cumulative Update 23",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.00.0",
"lessThan": "15.00.1497.012",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2013 Service Pack 1 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2013 Service Pack 1",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.00.0",
"lessThan": "15.00.0847.064",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 10 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 10",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1531.012",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 11 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 11",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1591.018",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 12 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 12",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1713.010",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 13 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 13",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1779.008",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 14 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 14",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1847.012",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 15 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 15",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1913.012",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 16 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 16",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1979.008",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 17 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 17",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.2044.013",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 18 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 18",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.2106.013",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 19 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 19",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.2176.009",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 8 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 8",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1415.010",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2016 Cumulative Update 9 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2016 Cumulative Update 9",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.01.0",
"lessThan": "15.01.1466.016",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0221.018",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 1 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 1",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.01.1979.006",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 2 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 2",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0397.011",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 3 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 3",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0464.015",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 4 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 4",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0659.012",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 5 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 5",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0595.008",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 6 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 6",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0529.013",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 7 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 7",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0721.013",
"versionType": "custom",
"status": "affected"
}
]
} Microsoft Exchange Server 2019 Cumulative Update 8 Vendor product
Publisher's version information Shown as published. These rules are not interpreted as NuGet package version ranges.
{
"vendor": "Microsoft",
"product": "Microsoft Exchange Server 2019 Cumulative Update 8",
"platforms": [
"x64-based Systems"
],
"versions": [
{
"version": "15.02.0",
"lessThan": "15.02.0792.010",
"versionType": "custom",
"status": "affected"
}
]
} Original source record · Cite this exact observation · Complete original publisher JSON