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PatchSiren cyber security CVE debrief

CVE-2026-55007 Microsoft CVE debrief

A double free vulnerability in Microsoft Exchange Server allows an unauthorized attacker to execute code over a network. The CVE record was published on 2026-09-08T18:17:41.820Z and has not been modified since then. The NVD entry is currently Analyzed. Defenders should assess potential exposure and prioritize patching or compensating controls, especially for versions 2019 Cumulative Update 14 and 2019 Cumulative Update 15. This vulnerability poses a significant risk due to its high severity and potential for code execution.

Vendor
Microsoft
Product
Exchange Server
CVSS
HIGH 8.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-10-05
Advisory published
2026-09-08
Advisory updated
2026-10-05

Who should care

Defenders responsible for Microsoft Exchange Server installations, especially those using versions 2019 Cumulative Update 14 and 2019 Cumulative Update 15, should assess potential exposure and prioritize patching or compensating controls.

Why it matters

The CVE-2026-55007 vulnerability in Microsoft Exchange Server allows an unauthorized attacker to execute code over a network, posing a significant risk to defenders. The vulnerability has a CVSS score of 8.1 and is considered HIGH severity. Defenders should prioritize verifying exposure, assessing the need for patches or compensating controls, and monitoring for potential exploitation attempts.

  • Verify Exchange Server installations for potential exposure.
  • Assess the need for patches or compensating controls.
  • Monitor for potential exploitation attempts.

Technical summary

The CVE-2026-55007 vulnerability is a double free issue in Microsoft Exchange Server that allows an unauthorized attacker to execute code over a network. The vulnerability has a CVSS score of 8.1 and is considered HIGH severity. It affects Microsoft Exchange Server, particularly versions 2019 Cumulative Update 14 and 2019 Cumulative Update 15. Defenders should prioritize verifying exposure and assessing the need for patches or compensating controls.

Defensive priority

Defenders should prioritize verifying exposure of Exchange Server installations, especially versions 2019 Cumulative Update 14 and 2019 Cumulative Update 15, and assess the need for patches or compensating controls.

Recommended defensive actions

  • Verify Exchange Server installations for potential exposure, especially versions 2019 Cumulative Update 14 and 2019 Cumulative Update 15.
  • Assess the need for patches or compensating controls based on the vendor advisory.
  • Monitor for potential exploitation attempts and adjust defensive measures accordingly.

Evidence notes

The CVE record and NVD detail page provide information on the vulnerability, but do not specify which versions are affected or provide details on exploitation. The vendor advisory provides patch information.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-55007 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-55007

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-55007 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-55007

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.