138 lines
8.4 KiB
JSON
138 lines
8.4 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-93127",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-09-17T16:02:15.087Z",
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"datePublished": "2026-09-17T16:11:31.253Z",
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"dateUpdated": "2026-10-19T09:06:00.545Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-19T09:06:00.545Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Drop scalar id on sign-extending narrowing stack fills\n\nWhen a spilled scalar is filled back with a sign-extending narrowing load\n(BPF_MEMSX), check_stack_read_fixed_off() copies the spilled register\nincluding its scalar id, but coerce_reg_to_size_sx() then sign-extends the\nfilled register's value. If the same slot is also filled with a plain\nzero-extending load (BPF_MEM), both destination registers share the id yet\nhold different values. A later 'if <zext-reg> == const' then refines the\nsign-extended register through sync_linked_regs() to a value it does not\nhave at runtime (e.g. the verifier believes 0x80000000 while the register\nis 0xffffffff80000000), which can be turned into an out-of-bounds access.\n\nDrop the shared scalar id at the sign-extension site in check_mem_access()\nwhen sign extension actually changes the value, mirroring the BPF_MOVSX\nhandling in check_alu_op() (no_sext = reg_umax < 2^(size*8-1))."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - The attacker-controlled input is BPF bytecode supplied via bpf(BPF_PROG_LOAD) in SYSCALL_DEFINE5(bpf) → bpf_prog_load() → bpf_check() → do_check_insn(); the bug fires on local BPF_LDX BPF_MEMSX/BPF_MEM stack fills in check_mem_access(), not on a remote protocol message.\nAC:L - The attacker writes the instruction sequence; ldsx_fill_scalar_id_not_shared deterministically spills a u32 with bit 31 set, fills it with *(s32*) into r4 and *(u32*) into r5, then uses if r5 == 0x80000000 so sync_linked_regs() poisons r4, with no race or external state.\nPR:L - check_stack_write_fixed_off()/check_stack_read_fixed_off() only preserve spilled scalar ids when env->bpf_capable, set from bpf_token_capable(CAP_BPF) in bpf_check(); unprivileged socket-filter loads therefore miss this path. CAP_BPF is delegable into a user namespace via bpf_token_create(), so this is Low, not init-namespace root.\nUI:N - The attacker loads the crafted program with bpf(BPF_PROG_LOAD), creates the hash map, and triggers bpf_map_lookup_elem plus the MEMSX/MEM fills themselves; no other user must mount media, open a file, or otherwise act.\nS:U - The confused r4 offset is applied to a PTR_TO_MAP_VALUE from bpf_map_lookup_elem() and corrupts host kernel heap in the same security authority; this is a verifier-bypass local privilege escalation, not a KVM/IOMMU guest-to-host crossing.\nC:H - After sync_linked_regs() copies known 0x80000000 onto the sign-extended r4 (runtime 0xffffffff80000000), r4 >>= 63 is believed 0 but is 1, so r0 += r4; *(u8*)(r0+7) on the 8-byte map value is an accepted out-of-bounds kernel read; repeating r0 += r4 yields an arbitrary-length read primitive.\nI:H - The same false r4==0 bound lets the verifier accept a store through that map-value pointer (replace the *(u8*)(r0+7) load with a store); repeating r0 += r4 before the store is an arbitrary kernel heap write usable for control-flow hijacking.\nA:H - The accepted program performs an out-of-bounds access on the bpf_map_lookup_elem() result (the selftest is rejected after the fix with \"R0 max value is outside of the allowed memory range\"); that heap OOB can oops or panic the kernel."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"kernel/bpf/verifier.c"
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],
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"versions": [
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{
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"version": "3cd5c890652ba1f0682adc291b5446245259b692",
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"lessThan": "f3614622dc41f3dd99bb4f691da253814e4e6cae",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "3cd5c890652ba1f0682adc291b5446245259b692",
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"lessThan": "2cb5f4ca695ebe552647e5ba4aad6934d6a43bae",
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"status": "affected",
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"versionType": "git"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"kernel/bpf/verifier.c"
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],
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"versions": [
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{
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"version": "7.0",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "7.0",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2.6",
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"lessThanOrEqual": "7.2.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.3",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "7.0",
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"versionEndExcluding": "7.2.6"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "7.0",
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"versionEndExcluding": "7.3"
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}
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]
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/f3614622dc41f3dd99bb4f691da253814e4e6cae"
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},
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{
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"url": "https://git.kernel.org/stable/c/2cb5f4ca695ebe552647e5ba4aad6934d6a43bae"
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}
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],
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"title": "bpf: Drop scalar id on sign-extending narrowing stack fills",
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"x_generator": {
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"engine": "bippy-1.2.0"
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