VulnerabilityPublished 12 Sep 2023Updated 30 Oct 2025

CVE-2023-36777: Microsoft Exchange Server 2019 Cumulative Update 12 · Deserialization of Untrusted Data

Affects Microsoft Exchange Server 2019 Cumulative Update 12Source CVE Database V5

Not known to be exploited · 52% EPSS · CVSS 5.7 Medium.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.7Medium

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

EPSS: 52.0% chance of exploitation in 30 days – higher than 98% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Base metrics

Attack Vector: Adjacent
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
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: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within 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 Sep 2023
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 2019 Cumulative Update 12	Affected =15.02.0	Fixed in–

AI-suggested

To mitigate CVE-2023-36777, European organizations should: 1) Monitor Microsoft security advisories closely and apply patches or cumulative updates as soon as Microsoft releases them for this vulnerability. 2) Restrict access to Exchange Server management and administrative interfaces to trusted networks and users using network segmentation and firewall rules. 3) Enforce strong authentication and authorization controls, including multi-factor authentication (MFA) for all Exchange-related accounts to reduce the risk of credential compromise. 4) Implement robust monitoring and logging of Exchange server activities, focusing on deserialization-related processes and unusual access patterns to detect potential exploitation attempts early. 5) Conduct regular security audits and vulnerability assessments on Exchange servers to identify and remediate misconfigurations or outdated software versions. 6) Educate IT staff about the risks associated with deserialization vulnerabilities and ensure secure coding and configuration practices are followed. 7) Consider deploying application-layer protections such as web application firewalls (WAFs) that can detect and block suspicious payloads targeting deserialization flaws. These measures collectively reduce the attack surface and improve detection capabilities until patches are applied.

Description

Microsoft Exchange Server Information Disclosure Vulnerability

Impact

For European organizations, the impact of CVE-2023-36777 could be substantial due to the widespread use of Microsoft Exchange Server 2019 in enterprise environments. Information disclosure could lead to leakage of sensitive corporate communications, intellectual property, or personal data of employees and customers, potentially violating GDPR and other data protection regulations. This could result in reputational damage, regulatory fines, and loss of customer trust. The vulnerability requires low privileges but authenticated access, so insider threats or compromised accounts could be leveraged to exploit it. The lack of impact on integrity and availability reduces the risk of service disruption or data manipulation, but confidentiality breaches alone can have serious consequences. Organizations relying heavily on Exchange for internal and external communications, especially in sectors such as finance, government, healthcare, and critical infrastructure, face elevated risks. The medium severity rating suggests that while the vulnerability is not critical, it should be addressed promptly to prevent escalation or combined attacks.

CWE-502Deserialization of Untrusted Data (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #15OWASP Top 10 A08:2025: Software or Data Integrity Failures (opens in a new tab)
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
Architecture and Design · Implementation
If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
Implementation
When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
Implementation
Explicitly define a final object() to prevent deserialization.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
XML Security (opens in a new tab)
XML External Entity Prevention (opens in a new tab)
Software Supply Chain Security (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.2 (opens in a new tab)
V5.5.3 (opens in a new tab)
V5.5.1 (opens in a new tab)
Attack patterns
Object Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2023-36777 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2025, 19:01 UTC

WeaknessesCWE-502

Technical details

References

Community reviews

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