CVE-2023-21529
Microsoft Exchange Server: Deserialization of Untrusted Data
As of , CVE-2023-21529 in Microsoft Exchange Server is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch now.
- Exploited
- Yes: CISA listed it on 13 April 2026
- US federal deadline
- 27 April 202614 days after CISA listed it. US federal civilian agencies must fix it by then.
- Used in ransomware campaigns
- KnownCISA changed it from Unknown to Known on 21 April 2026.
- EPSS score
- 0.59Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
- Public exploit
- None foundNeither Metasploit nor Exploit-DB lists one.
- Fix
- Vendor advice: msrc.microsoft.comLinks below, from CISA's entry.
What CISA says to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA's required action
What the flaw is
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
CISA's description
Microsoft Exchange Server Remote Code Execution Vulnerability
The CVE record's description, from microsoft
- CVE published
- 14 February 2023
- Assigned by
- microsoft
- CVSS
- 8.8 High (CVSS 3.1, from the CNA)
- CWE-502
- Deserialization of Untrusted Data
- CISA SSVC, exploitation
- active
- CISA SSVC, automatable
- no
- CISA SSVC, technical impact
- total
Timeline
- The CVE record was published.
- CISA added it to its list of exploited vulnerabilities.
- CISA changed its entry. Ransomware use: Unknown to Known.
- The US federal deadline to fix it.
Exchange Server: other exploited entries
| Vulnerability | Product | Our group | Listed | Deadline | EPSS |
|---|---|---|---|---|---|
| CVE-2020-0688Validation Key Remote Code Execution | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99; verified Exploit-DB entry | 0.99 | ||
| CVE-2022-41040Server-Side Request Forgery | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2022-41082Remote Code Execution | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2021-26855Remote Code Execution | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2021-27065Remote Code Execution | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2021-31207Security Feature Bypass | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2021-34473Remote Code Execution | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2021-34523Privilege Escalation | Microsoft Exchange Server | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2022-41080Privilege Escalation | Microsoft Exchange Server | Patch this weekRansomware use; EPSS 0.77 | 0.77 | ||
| CVE-2021-33766Information Disclosure | Microsoft Exchange Server | Patch this weekEPSS 0.98 | 0.98 |
Read further
- CVE recordcve.org
- NVD entrynvd.nist.gov
- CISA's catalogcisa.gov
- EPSS for this CVEapi.first.org