CVE-2026-55005 — Exchange Server
HIGHCVE-2026-55005 is a high-severity (CVSS 8.8) CWE-122 vulnerability in microsoft exchange server. A fix is available — see the affected versions and patch details below.
Heap-based buffer overflow in Microsoft Exchange Server allows an authorized attacker to execute code over a network.
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55005.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-55005 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Description
Heap-based buffer overflow in Microsoft Exchange Server allows an authorized attacker to execute code over a network.
Affected Products
exchange servermicrosoftexchange server subscription editionmicrosoftDetection & mitigation playbook
Vendor / applianceDetect
Inventory every microsoft exchange server deployment and check each version against the affected-products list above.
Fix
Apply the microsoft exchange server security patch or hotfix for CVE-2026-55005 on the affected version, following the vendor advisory for your exact build.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
Frequently Asked Questions
Is CVE-2026-55005 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.