What is the CVSS score of CVE-2017-8621?

CVE-2017-8621 has a CVSS 3.0 base score of 6.1 (Medium). CVSS vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 1.1%.

Is there a patch available for CVE-2017-8621?

Yes, a patch is available for CVE-2017-8621. Update the affected software to the latest version immediately.

Exchange Server CVE-2017-8621

MEDIUM

URL Redirection to Untrusted Site (Open Redirect) (CWE-601)

2017-07-11 secure@microsoft.com

Open Redirect Microsoft Exchange Server

6.1

CVSS 3.0 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-601 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V3 - Web Frontend Security Redirect URL validation MITRE ATT&CK 1 technique across 1 tactic: Initial Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 6.1 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, user interaction required. EPSS exploitation probability: 1.06%.
Exploit ScenarioDerived	A remote attacker could redirect users to malicious websites via URL manipulation by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Patch available 1.1% exploitation probability (EPSS)

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AnalysisAI

Microsoft Exchange Server 2010 SP3, Exchange Server 2013 SP3, Exchange Server 2013 CU16, and Exchange Server 2016 CU5 allows an open redirect vulnerability that could lead to spoofing, aka "Microsoft. Rated medium severity (CVSS 6.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Validate redirect destinations against an allowlist, avoid using user input in redirect URLs.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Open Redirect (CWE-601), which allows attackers to redirect users to malicious websites via URL manipulation. Microsoft Exchange Server 2010 SP3, Exchange Server 2013 SP3, Exchange Server 2013 CU16, and Exchange Server 2016 CU5 allows an open redirect vulnerability that could lead to spoofing, aka "Microsoft Exchange Open Redirect Vulnerability". Affected products include: Microsoft Exchange Server.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 6.1 MEDIUM

AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

DescriptionCVE.org

Threat Intelligence Overview

EPSS Score

1.1%

Top 22% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC No

EPSS 1.1%

Patch available Yes

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +1

CVSS: +30

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Affected Products (CPE)CVE.org

cpe:2.3:a:microsoft:exchange_server:2010:sp3:*:*:*:*:*:*

cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_16:*:*:*:*:*:*

cpe:2.3:a:microsoft:exchange_server:2013:sp1:*:*:*:*:*:*

cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_5:*:*:*:*:*:*

More in Exchange Server

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9.1 Jul 14

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9.1 Mar 03

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7.8 Mar 03

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8.8 Nov 10

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7.8 Mar 03

Microsoft Exchange Server allows authenticated attackers to write arbitrary files to the server filesystem, the third co

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8.8 Feb 14

Remote code execution in Microsoft Exchange Server 2013, 2016, and 2019 allows authenticated attackers to execute arbitr

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7.8 Mar 03

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7.2 Jul 14

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Same weakness CWE-601 – URL Redirection to Untrusted Site (Open Redirect)

View all

CVE-2017-1000117 HIGH POC

8.8

CVE-2016-5385 HIGH POC

8.1

CVE-2018-11784 MEDIUM POC

4.3

CVE-2017-3528 MEDIUM POC

5.4

CVE-2012-0518 MEDIUM

4.7

CVE-2024-21641 MEDIUM POC

6.5

CVE-2015-5354 MEDIUM POC

5.8

CVE-2024-22891 CRITICAL POC

9.8

References

Advisories & patches

PATCH https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8621 REF http://www.securityfocus.com/bid/99533 REF http://www.securitytracker.com/id/1038852

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GitHub PoC

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