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Researchers from MIT CSAIL disclosed an interrupt injection attack that can bypass Linux’s Safe RET mitigation for Spectre-class attacks on AMD Zen 1 through Zen 4 processors, potentially allowing information disclosure from kernel memory. AMD acknowledged the issue in its Return Address Security Bulletin and said the weakness stems from Linux’s implementation of the mitigation for Speculative Return Stack Overflow (SRSO) rather than the processor architecture alone. The flaw lets an attacker with code execution on a target system precisely time an interrupt to disrupt branch predictor sanitization and weaken the intended protection.
Linux has already patched the issue in the latest kernel Git code by addressing the handling of interrupts around the Safe RET mitigation path. The researchers reported demonstrating arbitrary kernel memory leakage on AMD Zen 2 systems running Linux with default Spectre v2 defenses, achieving 5.47 bytes per second at 91.97% accuracy and reading /etc/shadow in five of ten attempts. The work was reported by Daniël Trujillo of MIT CSAIL, presented at Black Hat USA, and accompanied by a proposed fix that adds a second predictor neutralization step on interrupt return; researchers also said related misprediction behavior was observed on some Intel systems, though AMD is the vendor that formally assigned and documented the vulnerability.
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The Safe RET Interrupt Vulnerability was publicly disclosed, with AMD and media reports describing how a precisely timed interrupt could disrupt Linux's Safe RET mitigation. The disclosure identified Zen 1 and Zen 2 as demonstrated targets and noted Zen 3 and Zen 4 could also be affected.
AMD published security bulletin AMD-SB-7061, titled "Safe RET Interrupt Vulnerability," describing an interrupt injection issue affecting Linux's Safe RET mitigation for SRSO on Zen 1 through Zen 4 processors. AMD said the issue appears tied to Linux's implementation and could enable information disclosure if exploited.
MIT CSAIL researchers Daniël Trujillo and Mengjia Yan demonstrated the TONTOU/Interrupt Injection attack against Linux on AMD Zen 2, leaking arbitrary kernel memory at 5.47 bytes per second and extracting /etc/shadow in 5 of 10 runs. They presented the findings at Black Hat USA, showing how the technique bypasses Spectre v2 mitigations by re-poisoning branch prediction state after mitigation cleanup.
A mitigation patch for the Safe RET Interrupt Vulnerability was added to the latest Linux kernel Git code. The change improved SRSO-related kernel handling to address the interrupt window in Linux's Safe RET implementation.
MIT CSAIL researchers Daniël Trujillo and Mengjia Yan disclosed the INTERRUPT INJECTION issue to AMD and Intel. The disclosure occurred on February 5, according to The Hacker News.
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Researchers disclosed the **Meltdown** and **Spectre** hardware flaws, showing that speculative execution in modern processors could let attackers read sensitive data across security boundaries on affected devices. Reuters reported that **Meltdown** primarily affected Intel processors by breaking memory isolation, while **Spectre** impacted Intel, AMD, and ARM chips by tricking applications into leaking secrets such as passwords and other protected data. CERT/CC later summarized the broader issue as cache side-channel attacks against CPU hardware using speculative execution, underscoring that the weakness was architectural rather than limited to a single product line. Major vendors and cloud providers moved to contain the fallout with software, firmware, and microcode mitigations, including Microsoft Azure protections for hosted customers and public advisories from manufacturers such as Huawei. Subsequent research showed the problem persisted beyond the initial disclosures: the **ZombieLoad** attacks demonstrated additional Intel data-leakage paths tied to speculative execution, and a later **TSX Asynchronous Abort (TAA)** variant affected some processors previously thought to be resistant. Intel issued microcode updates, but researchers and vendors warned that mitigations reduced rather than eliminated risk, that exploitation generally required local code execution, and that fully disabling the underlying CPU behavior would carry significant performance costs.
Jun 29, 2026
Researchers at **CISPA Helmholtz Center for Information Security** disclosed **StackWarp** (**CVE-2025-29943**), a microarchitectural weakness affecting **AMD Zen** CPUs that can undermine the integrity guarantees of **AMD SEV-SNP** “confidential VM” protections. The attack model assumes a **malicious insider with host/hypervisor control** who can run a parallel hyperthread and exploit a previously undocumented hypervisor-side control bit to manipulate the protected guest’s stack pointer behavior, particularly when **Simultaneous Multithreading (SMT)** is enabled. Reported impacts include the ability to recover sensitive data from SEV-SNP guests—such as **cryptographic private keys**—and to enable follow-on compromise scenarios like **bypassing OpenSSH password authentication** and **privilege escalation** within the VM. AMD issued patches (made available in **July 2025**) and later published a security bulletin rating the issue **low severity**, but the disclosure highlights ongoing risk that confidential computing isolation can be weakened by CPU-level behaviors; organizations running SEV-SNP should prioritize applying AMD’s updates and review SMT-related exposure in multi-tenant or high-trust boundary environments.
Jun 29, 2026
Microsoft disclosed and patched **CVE-2023-20588**, an AMD processor information disclosure vulnerability known as **AMD Speculative Leaks**, after including mitigations in its December 2023 security updates. The flaw affects multiple AMD CPU families, including **EPYC**, **Athlon**, and **Ryzen 3000-series** processors, and stems from divide-by-zero behavior that can cause the processor to transiently return random or stale data during speculative execution. The issue requires **local access** to exploit, but it was treated as a high-severity risk because sensitive data could be exposed from affected systems. Microsoft and CSIRT.SK said the vulnerability was identified by researchers from **Microsoft Azure Research** and **Vrije Universiteit Amsterdam**, and they urged organizations to apply Windows updates promptly. Guidance also advised developers to avoid using privileged data in divide-by-zero operations and to follow secure coding practices to reduce exposure.
Jul 24, 2026