EUVD-2026-56414
GHSA-97wg-gxw5-r3h4
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Network-accessible Exchange endpoint, low complexity, but PR:L required as description specifies an authorized attacker; no confidentiality or integrity impact, only high availability disruption.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
3DescriptionCVE.org
Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to deny service over a network.
AnalysisAI
Microsoft Exchange Server's handling of serialized data exposes organizations running Exchange 2016 CU23, Exchange 2019 CU14/CU15, and Exchange Subscription Edition to denial-of-service attacks from low-privileged, network-authenticated users. An authorized attacker exploiting this CWE-502 deserialization flaw can disrupt Exchange availability without requiring elevated permissions, potentially taking down email infrastructure for all dependent users and connected services. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a valid, low-privileged account within the target Exchange organization - the CVSS PR:L metric confirms that some level of authorization is required, consistent with the description's explicit reference to an 'authorized attacker.' The attack is conducted entirely over the network (AV:N) with no user interaction (UI:N) and low complexity (AC:L), meaning no special timing, race conditions, or secondary tooling are needed beyond delivering a crafted serialized payload. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 6.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) accurately reflects the constrained scope of this vulnerability: network-accessible, low complexity, but gated behind authenticated low-privilege access and limited entirely to an availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker holding any valid Exchange mailbox account authenticates to the Exchange server over the network and submits a crafted, maliciously structured serialized payload - for example via Exchange Web Services or another deserialization-exposed endpoint. The payload causes the Exchange backend process to encounter an unhandled exception or exhaust resources during object deserialization, crashing or hanging the service and rendering it unavailable to all users. … |
| Remediation | Microsoft has released patches for all affected Exchange Server versions. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-502 – Deserialization of Untrusted Data
View allSame technique Deserialization
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External POC / Exploit Code
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