CVE-2025-25007VulnerabilityPublished 12 Aug 2025Updated 13 Feb 2026

CVE-2025-25007: Microsoft Exchange Server 2016 Cumulative Update 23 · Improper Validation of Syntactic Correctness of Input

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, 06:26 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 58% 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 2026-10-26.

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 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

To mitigate CVE-2025-25007, European organizations should first verify their Exchange Server versions and prioritize upgrading to patched versions once Microsoft releases an official fix. In the interim, organizations can implement strict email authentication protocols such as SPF, DKIM, and DMARC to reduce the effectiveness of spoofed emails. Network segmentation and monitoring should be enhanced to detect anomalous traffic patterns indicative of spoofing attempts. Deploying advanced email security gateways with heuristic and signature-based detection can help identify and quarantine suspicious messages. Administrators should audit and harden Exchange Server configurations, disabling unnecessary services and enforcing strict input validation rules where possible. Regular security awareness training for employees can reduce the risk of social engineering attacks stemming from spoofed communications. Additionally, organizations should maintain comprehensive logging and alerting to quickly identify and respond to potential exploitation attempts. Collaboration with ISPs and email providers to trace and block spoofed sources can further reduce exposure. Finally, organizations should review incident response plans to include scenarios involving spoofing and impersonation attacks.

Description

Improper validation of syntactic correctness of input in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

Impact

For European organizations, the primary impact of CVE-2025-25007 lies in the potential compromise of communication integrity within and outside the enterprise. Spoofing attacks can lead to unauthorized information disclosure, manipulation of email content, or impersonation of trusted contacts, which may facilitate phishing, fraud, or lateral movement within networks. Disruption of email trust can erode confidence in internal and external communications, potentially affecting business operations and compliance with data protection regulations such as GDPR. Organizations relying on Microsoft Exchange Server 2016 CU23 are at risk, especially those with high volumes of sensitive or regulated communications. The vulnerability does not directly affect confidentiality or availability but can indirectly lead to broader security incidents if attackers leverage spoofed identities to escalate privileges or deploy malware. The lack of required authentication and user interaction lowers the barrier for exploitation, increasing the threat surface. European sectors with critical infrastructure, finance, healthcare, and government entities using Exchange Server are particularly vulnerable to targeted spoofing campaigns that could disrupt services or lead to data breaches.

CWE-1286Improper Validation of Syntactic Correctness of Input (opens in a new tab)
Base weakness
The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.
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.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
SQL Injection (opens in a new tab)
NoSQL Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2025-25007 (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-1286

Technical details

References

Community reviews

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