VulnerabilityPublished 12 Aug 2025Updated 13 Feb 2026

CVE-2025-25006: Microsoft Exchange Server 2016 Cumulative Update 23 · Improper Handling of Additional Special Element

Affects Microsoft Exchange Server 2016 Cumulative Update 23Source CVE Database V5

Not known to be exploited · CVSS 5.3 Medium.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.8% chance of exploitation in 30 days – higher than 59% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C

Base metrics

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Temporal metrics

Exploit Code Maturity: Unproven
Remediation Level: Official Fix
Report Confidence: Confirmed

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.
Exploit Code Maturity: Unproven: No exploit code is available, or an exploit is theoretical.
Remediation Level: Official Fix: A complete vendor solution is available. Either the vendor has issued an official patch, or an upgrade is available.
Report Confidence: Confirmed: Detailed reports exist, or functional reproduction is possible (functional exploits may provide this). Source code is available to independently verify the assertions of the research, or the author or vendor of the affected code has confirmed the presence of the vulnerability.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Microsoft Microsoft Exchange Server 2016 Cumulative Update 23	Affected =15.01.0.0	Fixed in–

AI-suggested

Apply Microsoft security updates or patches for Exchange Server 2016 CU23 as soon as they are released to address CVE-2025-25006.
Implement strict email authentication mechanisms such as SPF, DKIM, and DMARC to reduce the effectiveness of spoofed emails.
Monitor network traffic and Exchange Server logs for unusual or anomalous activity that may indicate spoofing attempts or exploitation attempts.
Restrict external access to Exchange Server management interfaces and enforce network segmentation to limit exposure.
Employ advanced threat detection tools that can identify spoofing or impersonation behaviors in email and network communications.
Conduct user awareness training focused on recognizing phishing and spoofing attempts to reduce the risk of social engineering attacks leveraging this vulnerability.
Regularly review and update firewall and intrusion detection/prevention system (IDS/IPS) rules to detect and block suspicious traffic patterns related to spoofing.
Consider deploying network-level protections such as TLS enforcement and certificate validation to strengthen communication integrity.

Description

Improper handling of additional special element in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

Impact

For European organizations, the primary impact of CVE-2025-25006 is the potential for network spoofing attacks that can undermine the integrity of email communications and network traffic within corporate environments. This can lead to successful phishing campaigns, business email compromise (BEC), or lateral movement by attackers who exploit spoofed identities to bypass security controls or gain unauthorized access. While the vulnerability does not directly affect confidentiality or availability, the integrity compromise can indirectly lead to data breaches or operational disruptions if attackers leverage spoofed messages to deploy malware or exfiltrate data. Organizations with large deployments of Microsoft Exchange Server 2016 CU23, especially in sectors such as finance, government, healthcare, and critical infrastructure, face elevated risks. The medium severity rating suggests a moderate but non-negligible threat that requires timely remediation to prevent exploitation. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the potential for future attacks as threat actors develop capabilities to leverage this flaw.

CWE-167Improper Handling of Additional Special Element (opens in a new tab)
Base weakness
The product receives input from an upstream component, but it does not handle or incorrectly handles when an additional unexpected special element is provided.
Developers should anticipate that extra special elements will be injected in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Implementation · Output Encoding
While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
V5.2.2 (opens in a new tab)
V5.2.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2025-25006 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Feb 2026, 10:34 UTC

WeaknessesCWE-167

Technical details

References

Community reviews

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