{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-11985",
        "assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
        "state": "PUBLISHED",
        "assignerShortName": "zephyr",
        "dateReserved": "2026-06-11T14:04:09.251Z",
        "datePublished": "2026-08-11T04:56:59.359Z",
        "dateUpdated": "2026-08-31T23:13:18.528Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
                "shortName": "zephyr",
                "dateUpdated": "2026-08-31T23:13:18.528Z"
            },
            "title": "Cross-thread FPU register leak on ARM when FPU enabled without register sharing",
            "descriptions": [
                {
                    "lang": "en",
                    "value": "On the Zephyr ARM port, enabling the hardware FPU (CONFIG_FPU) forces the \"Floating point ABI\" choice, which defaults to CONFIG_FP_HARDABI. Both FP_HARDABI and FP_SOFTABI permit the compiler to emit hardware FP instructions in any function, even code that never uses floating-point types. However, the callee-saved FP registers (s16-s31 / d8-d15) are only saved and restored across a context switch when CONFIG_FPU_SHARING is enabled (arch/arm/core/cortex_m/swap_helper.S and arch/arm/core/cortex_a_r/swap_helper.S), and prior to this fix selecting an ABI did not enable FPU register sharing, which defaults off.\n\nIn a build that enables the FPU with the default ABI but leaves CONFIG_FPU_SHARING disabled, the kernel preserves no callee-saved FP register state across thread switches. The documented precondition for this \"unshared\" mode — that only a single thread ever executes FP instructions — is silently violated because the compiler may generate FP instructions in every thread.\n\nUnder CONFIG_USERSPACE, where threads are mutually isolated, this becomes an information-disclosure boundary crossing: a victim thread can leave secret-derived values in s16-s31, and a co-resident unprivileged thread can read those registers directly (FP register access is not privilege-gated), recovering data left behind by another thread. Without userspace the same defect causes cross-thread FP state corruption (a correctness fault). The leak is bounded to the 16 callee-saved single-precision registers and is opportunistic, so impact is low.\n\nThe fix makes FP_HARDABI and FP_SOFTABI select CONFIG_FPU_SHARING and tags every thread with K_FP_REGS at creation, so callee-saved FP state is always preserved across context switches whenever the compiler may emit FP instructions."
                }
            ],
            "affected": [
                {
                    "vendor": "zephyrproject",
                    "product": "zephyr",
                    "collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
                    "packageName": "zephyr",
                    "defaultStatus": "unaffected",
                    "programFiles": [
                        "arch/Kconfig",
                        "arch/arm/core/Kconfig",
                        "arch/arm/core/cortex_a_r/thread.c",
                        "arch/arm/core/cortex_m/thread.c"
                    ],
                    "versions": [
                        {
                            "version": "1.13.0",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "4.4.2"
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://github.com/zephyrproject-rtos/zephyr/commit/3d405326a7653cba6860280e45c8734f8d3fc423",
                    "name": "Fix commit",
                    "tags": [
                        "patch"
                    ]
                },
                {
                    "url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-qxr9-wh3c-hvgv",
                    "name": "GHSA-qxr9-wh3c-hvgv"
                }
            ],
            "metrics": [
                {
                    "format": "CVSS",
                    "cvssV3_1": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N",
                        "baseScore": 3.6,
                        "baseSeverity": "LOW"
                    }
                }
            ],
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "lang": "en",
                            "description": "info-leak",
                            "cweId": "CWE-200",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "x_generator": {
                "engine": "cvelib 1.8.0"
            }
        },
        "adp": [
            {
                "metrics": [
                    {
                        "other": {
                            "type": "ssvc",
                            "content": {
                                "timestamp": "2026-08-11T17:55:04.091131Z",
                                "id": "CVE-2026-11985",
                                "options": [
                                    {
                                        "Exploitation": "none"
                                    },
                                    {
                                        "Automatable": "no"
                                    },
                                    {
                                        "Technical Impact": "partial"
                                    }
                                ],
                                "role": "CISA Coordinator",
                                "version": "2.0.3"
                            }
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                ],
                "title": "CISA ADP Vulnrichment",
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                    "shortName": "CISA-ADP",
                    "dateUpdated": "2026-08-11T17:55:22.188Z"
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}