YellowKey and GreenPlasma Windows zero-days disclosed; mitigations shared for BitLocker bypass

Microsoft has shared mitigations for YellowKey, a recently disclosed Windows BitLocker zero-day vulnerability that grants access to protected drives. [...]

It’s nasty, but it requires physical access to the computer: The exploit, named YellowKey, was published earlier this week by a researcher who goes by the alias Nightmare-Eclipse. It reliably bypasses default Windows 11 deployments of BitLocker, the full-volume encryption protection Microsoft provides to make disk contents off-limits to anyone without the decryption key, which is stored in a secured piece of hardware known as a trusted platform module (TPM). BitLocker is a mandatory protection for many organizations, including those that contract with governments...

An anonymous researcher known as Nightmare-Eclipse, who has already leaked several Windows zero-days this year, has disclosed two more: YellowKey and GreenPlasma. The Register reports: Nightmare-Eclipse described YellowKey as "one of the most insane discoveries I ever found." They provided the files, which have to be loaded onto a USB drive, and if the attacker completes the key sequence correctly, they are granted unrestricted shell access to a BitLocker-protected machine. When it comes to claims like these, we usually exercise some caution, as this bug requires physical access to a Windows PC. However, seeing that BitLocker acts as Windows' last line of defense for stolen devices, bypassing the technology grants thieves the ability to access encrypted files. Rik Ferguson, VP of security intelligence at Forescout, said: "If [the researcher's claim] holds up, a stolen laptop stops being a hardware problem and becomes a breach notification." Despite the physical access requirement, Gavin Knapp, cyber threat intelligence principal lead at Bridewell, told The Register that YellowKey remains "a huge security problem for organizations using BitLocker." Citing information shared in cyber threat intelligence circles, he added that YellowKey can be mitigated by implementing a BitLocker PIN and a BIOS password lock. Nightmare-Eclipse hinted at YellowKey also acting as a backdoor, allegedly injected by Microsoft, although the people we spoke to said this was impossible to verify based on the information available. The researcher also published partial exploit code for GreenPlasma, rather than a fully formed proof of concept exploit (PoC). Ferguson noted attackers need to take the code provided by the researcher and figure out how to weaponize it themselves, which is no small task: in its current state it triggers a UAC consent prompt in default Windows configurations, meaning a silent exploit remains a work in progress. Knapp warned that these kinds of privilege escalation flaws are often used by attackers after they gain an initial foothold in a victim's system. "These elevation of privilege vulnerabilities are often weaponized during post-exploitation to enable threat actors to discover and harvest credentials and data, before moving laterally to other systems, prior to end goals such as data theft and/or ransomware deployment," he said. "Currently, there is no known mitigation for GreenPlasma. It will be important to patch when Microsoft addresses the issue." The other zero-days leaked include RedSun, a Windows Defender privilege escalation flaw; UnDefend, a Windows Defender denial-of-service bug; and BlueHammer, a separate Microsoft vulnerability tracked as CVE-2026-32201 that was patched in April. According to The Register, RedSun and UnDefend remained unfixed at the time of publication, and proof-of-concept code for the flaws was reportedly picked up quickly and abused in real-world attacks. Read more of this story at Slashdot.

An anonymous cybersecurity researcher who disclosed three Microsoft Defender vulnerabilities has returned with two more zero-days involving a BitLocker bypass and a privilege escalation impacting Windows Collaborative Translation Framework (CTFMON). The security defects have been codenamed YellowKey and GreenPlasma, respectively, by the researcher, who goes by the online aliases Chaotic Eclipse

A cybersecurity researcher has published proof-of-concept (PoC) exploits for two unpatched Microsoft Windows vulnerabilities named YellowKey and GreenPlasma, which are a BitLocker bypass and a privilege-escalation flaw. [...]