Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2023-21529 is a high-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Microsoft Exchange Server. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Junk Data (T1001.001); ranked in the top 0.9% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2023-21529 is a remote code execution vulnerability in Microsoft Exchange Server that arises from unsafe deserialization of untrusted data, tracked under CWE-502. The flaw received a CVSS 3.1 base score of 8.8, driven by network attack vector, low attack complexity, and low privileges required, with high impact across confidentiality, integrity, and availability.
An authenticated attacker with low privileges can send specially crafted requests over the network to trigger arbitrary code execution on the Exchange server, enabling full control of the affected system without user interaction.
Microsoft security updates address the issue through the MSRC guidance portal, while CISA lists the CVE in its catalog of known exploited vulnerabilities, indicating that organizations should apply available patches as a priority.
The associated EPSS score reached a peak of 0.3668 and remains at 0.2704, and the vulnerability has been observed in active ransomware operations conducted by Storm-1175 against internet-facing assets.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-25697
Vulnerability Data
Microsoft Exchange Server Remote Code Execution Vulnerability
- CWE(s)
- KEV Date Added
- 13 April 2026
Related Threats
Threat-Actor AttributionAI
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Penetration testing supplies malicious serialized objects, detecting unsafe deserialization and supporting corrective actions.
Evaluation of untrusted data handling (deserialization testing) reveals unsafe processing, which the required remediation process addresses.
Untrusted serialized data can be deserialized and observed inside the chamber, blocking gadget-chain exploitation outside the sandbox.
Validates or rejects untrusted serialized data before deserialization occurs.
Identifies and blocks malicious code introduced through deserialization of untrusted data at system boundaries.
Integrity verification of serialized information can detect tampering before deserialization occurs.
Provenance of associated data allows detection of untrusted sources before deserialization or processing occurs.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
PR.PS-02 addresses only post-deployment updates/patching and cannot prevent introduction of unsafe deserialization code, yet it can remediate some instances when the flaw exists in outdated libraries or components.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.