{"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": "2026-08-11T04:56:59.359Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad", "shortName": "zephyr", "dateUpdated": "2026-08-11T04:56:59.359Z"}, "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 \u2014 that only a single thread ever executes FP instructions \u2014 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", "lessThanOrEqual": "4.4.1"}]}], "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"}}}}

{}

{}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.13.0,4.4.1]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "zephyr", "source": "cna", "vendor": "zephyrproject"}, "product": "zephyr", "vendor": "zephyrproject"}], "created": "2026-08-11T06:30:06.641786+00:00", "updated": "2026-08-11T06:30:06.735734+00:00", "vendors": ["zephyrproject", "zephyrproject$PRODUCT$zephyr"]}