CVE-2026-8948VulnerabilityPublished 14 Nov 2026

Microsoft · Same-origin Policy Bypass

Affects MicrosoftSource GCVE Database

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Authoritative record:CVE-2026-8948· Critical 9.1

Not known to be exploited · CVSS 9.1 Critical · patch available : patch Microsoft as a priority.

Data as of 14 Nov 2026, 09:17 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

microsoft-security-response-ce

What to do

Affected software

Product	Affected	Fixed in
Microsoft Security Response Center Microsoft	Affected <151	Fixed in 151

Description

CVE-2026-8948 is a vulnerability in Microsoft software version 4.0 involving a same-origin policy bypass in the DOM networking component. The same-origin policy is a critical security mechanism that restricts how documents or scripts loaded from one origin can interact with resources from another origin. This bypass could potentially allow unauthorized access to resources across origins. No CVSS score or detailed impact information is provided, and there is no indication of active exploitation in the wild.

Impact

The impact of this vulnerability is a potential security boundary bypass in the same-origin policy, which could allow unauthorized cross-origin interactions in the affected Microsoft software version 4.0. However, no specific exploitation or impact scenarios are documented, and no active exploitation is known.

Summary

This vulnerability, identified as CVE-2026-8948, affects Microsoft product version 4.0 and involves a bypass of the same-origin policy within the DOM networking component. The same-origin policy is designed to prevent malicious scripts on one origin from accessing sensitive data on another. A bypass could undermine this security boundary, potentially enabling cross-origin data access. The vulnerability is cataloged under CWE-942 (Improper Control of Object Lifecycle). Published information does not include a CVSS score, exploit details, or patch availability.

CWE-942Permissive Cross-domain Security Policy with Untrusted Domains (opens in a new tab)
Variant weaknessOWASP Top 10 A02:2025: Security Misconfiguration (opens in a new tab)
The product uses a web-client protection mechanism such as a Content Security Policy (CSP) or cross-domain policy file, but the policy includes untrusted domains with which the web client is allowed to communicate.
Architecture and Design · Operation · Attack Surface Reduction
Define a restrictive Content Security Policy or cross-domain policy file.
Architecture and Design · Operation · Attack Surface Reduction
Avoid using wildcards in the CSP / cross-domain policy file. Any domain matching the wildcard expression will be implicitly trusted, and can perform two-way interaction with the target server.
Architecture and Design · Operation · Environment Hardening
For Flash, modify crossdomain.xml to use meta-policy options such as 'master-only' or 'none' to reduce the possibility of an attacker planting extraneous cross-domain policy files on a server.
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V1.14.1 (opens in a new tab)
V13.4.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Nov 2026, 09:17 UTC

WeaknessesCWE-942

Technical details

References

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