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"cveId": "CVE-2021-46908",
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"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2024-02-25T13:45:52.718Z",
"datePublished": "2024-02-27T06:53:49.541Z",
"dateUpdated": "2026-08-05T08:44:59.893Z"
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Use correct permission flag for mixed signed bounds arithmetic\n\nWe forbid adding unknown scalars with mixed signed bounds due to the\nspectre v1 masking mitigation. Hence this also needs bypass_spec_v1\nflag instead of allow_ptr_leaks."
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"baseScore": 7.1,
"baseSeverity": "HIGH"
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"value": "AV:L - The vulnerable code is in the BPF verifier (adjust_ptr_min_max_vals), reached only via the local bpf() syscall when loading a program (e.g. SOCKET_FILTER), not via network packet processing.\nAC:L - An attacker can reliably craft and load a BPF program with mixed signed-bounds pointer arithmetic on PTR_TO_MAP_VALUE; no race or external environmental condition beyond the attacker's control is required to reach the buggy check. Unprivileged users can load BPF_PROG_TYPE_SOCKET_FILTER/CGROUP_SKB when kernel.unprivileged_bpf_disabled is 0 (upstream default throughout the 5.8–5.11 affected range), which exercises this verifier path without CAP_BPF or CAP_PERFMON. An attacker can reliably craft and load a BPF program with mixed signed-bounds pointer arithmetic on PTR_TO_MAP_VALUE; no race or external environmental condition beyond the attacker's control is required to reach the buggy check.\nPR:L - Unprivileged users can load BPF_PROG_TYPE_SOCKET_FILTER/CGROUP_SKB when kernel.unprivileged_bpf_disabled is 0 (upstream default throughout the 5.8–5.11 affected range), which exercises this verifier path without CAP_BPF or CAP_PERFMON.\nUI:N - Exploitation requires only the attacker loading their own BPF program; no victim action is needed.\nS:U - Impact stays within the kernel's security authority (local speculative disclosure of kernel memory); this is not a VM/IOMMU/sandbox boundary crossing.\nC:H - The check exists specifically for Spectre v1 masking of map-value pointer arithmetic; bypassing it enables speculative out-of-bounds access that can disclose arbitrary kernel memory via side channels, matching other BPF Spectre CVEs.\nI:N - This is a speculative-execution mitigation gap; architectural verifier bounds still apply and speculative effects do not commit writes, so integrity is not impacted.\nA:H - Same-series BPF Spectre sanitation bugs (e.g. CVE-2020-27171) and existing assessments of this CVE treat failed/incorrect ALU sanitation as potentially crashing the kernel; under the overestimate rule A:H is the higher-severity choice."
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"version": "2.0.3",
"timestamp": "2024-02-27T15:41:34.586719Z"
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