CVE-2026-21531
CVE-2026-21531 is a critical-severity vulnerability in Microsoft Azure Conversation Authoring Client Library with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.
Key facts
- Severity: Critical (CVSS 3.x base score 9.8)
- EPSS exploit prediction: 2% (82nd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-7338
- Weakness: CWE-502
- Affected product: Microsoft Azure Conversation Authoring Client Library
- Published:
- Last modified:
Description
Deserialization of untrusted data in Azure SDK allows an unauthorized attacker to execute code over a network.
Frequently asked questions
- What is CVE-2026-21531?
- Deserialization of untrusted data in Azure SDK allows an unauthorized attacker to execute code over a network.
- How severe is CVE-2026-21531?
- CVE-2026-21531 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-21531 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-21531?
- CVE-2026-21531 primarily affects Microsoft Azure Conversation Authoring Client Library. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2026-21531?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
- Does CVE-2026-21531 have an EU (EUVD) identifier?
- Yes. CVE-2026-21531 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7338.
- When was CVE-2026-21531 published?
- CVE-2026-21531 was published on 2026-02-10 and last updated on 2026-06-17.
References
Affected products (3)
- cpe:2.3:a:microsoft:azure_conversation_authoring_client_library:1.0.0:beta1:*:*:*:python:*:*
- cpe:2.3:a:microsoft:azure_conversation_authoring_client_library:1.0.0:beta2:*:*:*:python:*:*
- cpe:2.3:a:microsoft:azure_conversation_authoring_client_library:1.0.0:beta3:*:*:*:python:*:*
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