CVE-2026-42824

This issue is about a weakness in how Microsoft 365 Copilot handles certain inputs sent over the network. In simple terms: if someone figures out how to “trick” it, they may be able to get it to show information they shouldn’t. Think of it like slipping a note into a mailbox that changes how the mail gets read—if the system doesn’t properly handle that trick, private information can leak.

This matters to you if you use or run Microsoft 365 Copilot (listed as “microsoft copilot” and “Microsoft Microsoft 365 Copilot”). If your business relies on these tools to view or work with business content, you should treat this as a real data-protection concern. It’s not specific to a rare niche product—if you’re a Microsoft 365 Copilot customer, you’re in scope.

Do this soon—within the next few days—as this is an AMBER issue and press attention is rising due to a patch. Even though there’s no known public exploit and no evidence from CISA KEV that it’s widely exploited yet, there is a proof-of-concept publicly discussed, which means motivated attackers may start testing quickly. The practical goal is to ensure your tenant is updated and protected before anyone tries to use the trick.

1. Identify scope: confirm you are using Microsoft 365 Copilot (microsoft copilot / Microsoft Microsoft 365 Copilot) and whether any apps or workflows integrate Copilot with business data. 2) Apply Microsoft’s fix: check Microsoft’s security advisories/servicing guidance and confirm your Microsoft 365 tenant has received the relevant patch. If you manage updates through an admin process, verify completion. 3) Mitigations while waiting (if patch timing is uncertain): temporarily restrict Copilot access to fewer users, especially for users handling sensitive data; review any Copilot “connectors” or integrated content sources to ensure they’re not exposing unnecessary datasets. 4) Validate: after the update, confirm Copilot still functions normally and that there are no new errors that could indicate misconfiguration. 5) Monitor: have IT review audit and usage logs for anomalous Copilot requests (unusual patterns, repeated failed attempts, or unexpected access to specific content areas) and ensure standard incident-response steps are ready if anything suspicious is detected.

CVE-2026-42824 is an information disclosure flaw described as improper neutralization of special elements used in a command (command injection) in M365 Copilot. The described impact is unauthorized attackers disclosing information over a network. Provided context indicates: CVSS 6.5 (Medium), EPSS 0.5% estimated probability of exploitation in the next 30 days, CISA KEV “no” (not known to be exploited widely/confirmed via KEV), public exploit available “no,” and exploitation status in press described as “poc_public.” No Nuclei detection template exists. Translation for defenders: while it’s not confirmed as mass-exploited (no KEV, no public exploit), the presence of a public proof-of-concept means testing is plausible; therefore tenant patching and access controls should be prioritized.