{"id":"CVE-2026-45933","state":"PUBLISHED","title":"bpf: Preserve id of register in sync_linked_regs()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Preserve id of register in sync_linked_regs()\n\nsync_linked_regs() copies the id of known_reg to reg when propagating\nbounds of known_reg to reg using the off of known_reg, but when\nknown_reg was linked to reg like:\n\nknown_reg = reg         ; both known_reg and reg get same id\nknown_reg += 4          ; known_reg gets off = 4, and its id gets BPF_ADD_CONST\n\nnow when a call to sync_linked_regs() happens, let's say with the following:\n\nif known_reg >= 10 goto pc+2\n\nknown_reg's new bounds are propagated to reg but now reg gets\nBPF_ADD_CONST from the copy.\n\nThis means if another link to reg is created like:\n\nanother_reg = reg       ; another_reg should get the id of reg but\n                          assign_scalar_id_before_mov() sees\n                          BPF_ADD_CONST on reg and assigns a new id to it.\n\nAs reg has a new id now, known_reg's link to reg is broken. If we find\nnew bounds for known_reg, they will not be propagated to reg.\n\nThis can be seen in the selftest added in the next commit:\n\n0: (85) call bpf_get_prandom_u32#7    ; R0=scalar()\n1: (57) r0 &= 255                     ; R0=scalar(smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff))\n2: (bf) r1 = r0                       ; R0=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff)) R1=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff))\n3: (07) r1 += 4                       ; R1=scalar(id=1+4,smin=umin=smin32=umin32=4,smax=umax=smax32=umax32=259,var_off=(0x0; 0x1ff))\n4: (a5) if r1 < 0xa goto pc+4         ; R1=scalar(id=1+4,smin=umin=smin32=umin32=10,smax=umax=smax32=umax32=259,var_off=(0x0; 0x1ff))\n5: (bf) r2 = r0                       ; R0=scalar(id=2,smin=umin=smin32=umin32=6,smax=umax=smax32=umax32=255) R2=scalar(id=2,smin=umin=smin32=umin32=6,smax=umax=smax32=umax32=255)\n6: (a5) if r1 < 0xe goto pc+2         ; R1=scalar(id=1+4,smin=umin=smin32=umin32=14,smax=umax=smax32=umax32=259,var_off=(0x0; 0x1ff))\n7: (35) if r0 >= 0xa goto pc+1        ; R0=scalar(id=2,smin=umin=smin32=umin32=6,smax=umax=smax32=umax32=9,var_off=(0x0; 0xf))\n8: (37) r0 /= 0\ndiv by zero\n\nWhen 4 is verified, r1's bounds are propagated to r0 but r0 also gets\nBPF_ADD_CONST (bug).\nWhen 5 is verified, r0 gets a new id (2) and its link with r1 is broken.\n\nAfter 6 we know r1 has bounds [14, 259] and therefore r0 should have\nbounds [10, 255], therefore the branch at 7 is always taken. But because\nr0's id was changed to 2, r1's new bounds are not propagated to r0.\nThe verifier still thinks r0 has bounds [6, 255] before 7 and execution\ncan reach div by zero.\n\nFix this by preserving id in sync_linked_regs() like off and subreg_def.","publishedAt":"2026-05-27T12:17:51.127Z","updatedAt":"2026-10-19T19:26:39.760Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"58059335e46537de682db84984f7716c813208c4","versionType":"git"},{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"92a8cb1806adefb263cf096eab6705705cf7eee1","versionType":"git"},{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"65d114b5270b62aefb820ecd6c3b7caeea8f895d","versionType":"git"},{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"af9e89d8dd39530c8bd14c33ddf6b502df1071b6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/verifier.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.11","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.14","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.4","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/verifier.c"]}],"references":["https://git.kernel.org/stable/c/58059335e46537de682db84984f7716c813208c4","https://git.kernel.org/stable/c/92a8cb1806adefb263cf096eab6705705cf7eee1","https://git.kernel.org/stable/c/65d114b5270b62aefb820ecd6c3b7caeea8f895d","https://git.kernel.org/stable/c/af9e89d8dd39530c8bd14c33ddf6b502df1071b6"],"weaknesses":["CWE-682"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/45xxx/CVE-2026-45933.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-45933","state":"PUBLISHED","datePublished":"2026-05-27T12:17:51.127Z","dateUpdated":"2026-10-19T19:26:39.760Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-13T15:03:33.086Z"},"containers":{"cna":{"title":"bpf: Preserve id of register in sync_linked_regs()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Preserve id of register in sync_linked_regs()\n\nsync_linked_regs() copies the id of known_reg to reg when propagating\nbounds of known_reg to reg using the off of known_reg, but when\nknown_reg was linked to reg like:\n\nknown_reg = reg         ; both known_reg and reg get same id\nknown_reg += 4          ; known_reg gets off = 4, and its id gets BPF_ADD_CONST\n\nnow when a call to sync_linked_regs() happens, let's say with the following:\n\nif known_reg >= 10 goto pc+2\n\nknown_reg's new bounds are propagated to reg but now reg gets\nBPF_ADD_CONST from the copy.\n\nThis means if another link to reg is created like:\n\nanother_reg = reg       ; another_reg should get the id of reg but\n                          assign_scalar_id_before_mov() sees\n                          BPF_ADD_CONST on reg and assigns a new id to it.\n\nAs reg has a new id now, known_reg's link to reg is broken. If we find\nnew bounds for known_reg, they will not be propagated to reg.\n\nThis can be seen in the selftest added in the next commit:\n\n0: (85) call bpf_get_prandom_u32#7    ; R0=scalar()\n1: (57) r0 &= 255                     ; R0=scalar(smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff))\n2: (bf) r1 = r0                       ; R0=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff)) R1=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff))\n3: (07) r1 += 4                       ; R1=scalar(id=1+4,smin=umin=smin32=umin32=4,smax=umax=smax32=umax32=259,var_off=(0x0; 0x1ff))\n4: (a5) if r1 < 0xa goto pc+4         ; R1=scalar(id=1+4,smin=umin=smin32=umin32=10,smax=umax=smax32=umax32=259,var_off=(0x0; 0x1ff))\n5: (bf) r2 = r0                       ; R0=scalar(id=2,smin=umin=smin32=umin32=6,smax=umax=smax32=umax32=255) R2=scalar(id=2,smin=umin=smin32=umin32=6,smax=umax=smax32=umax32=255)\n6: (a5) if r1 < 0xe goto pc+2         ; R1=scalar(id=1+4,smin=umin=smin32=umin32=14,smax=umax=smax32=umax32=259,var_off=(0x0; 0x1ff))\n7: (35) if r0 >= 0xa goto pc+1        ; R0=scalar(id=2,smin=umin=smin32=umin32=6,smax=umax=smax32=umax32=9,var_off=(0x0; 0xf))\n8: (37) r0 /= 0\ndiv by zero\n\nWhen 4 is verified, r1's bounds are propagated to r0 but r0 also gets\nBPF_ADD_CONST (bug).\nWhen 5 is verified, r0 gets a new id (2) and its link with r1 is broken.\n\nAfter 6 we know r1 has bounds [14, 259] and therefore r0 should have\nbounds [10, 255], therefore the branch at 7 is always taken. But because\nr0's id was changed to 2, r1's new bounds are not propagated to r0.\nThe verifier still thinks r0 has bounds [6, 255] before 7 and execution\ncan reach div by zero.\n\nFix this by preserving id in sync_linked_regs() like off and subreg_def."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"58059335e46537de682db84984f7716c813208c4","versionType":"git"},{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"92a8cb1806adefb263cf096eab6705705cf7eee1","versionType":"git"},{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"65d114b5270b62aefb820ecd6c3b7caeea8f895d","versionType":"git"},{"version":"98d7ca374ba4b39e7535613d40e159f09ca14da2","status":"affected","lessThan":"af9e89d8dd39530c8bd14c33ddf6b502df1071b6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/verifier.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.11","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.14","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.4","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/verifier.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/58059335e46537de682db84984f7716c813208c4"},{"url":"https://git.kernel.org/stable/c/92a8cb1806adefb263cf096eab6705705cf7eee1"},{"url":"https://git.kernel.org/stable/c/65d114b5270b62aefb820ecd6c3b7caeea8f895d"},{"url":"https://git.kernel.org/stable/c/af9e89d8dd39530c8bd14c33ddf6b502df1071b6"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is in the BPF verifier, reached only by loading a crafted BPF program via the bpf() syscall from a local process; remote data never reaches this code.\nAC:L - The attacker writes the exact BPF instruction sequence that deterministically triggers the broken link in sync_linked_regs(); no race or uncontrolled condition is involved.\nPR:L - The verifier runs for all program loads, and socket-filter/cgroup-skb programs are loadable without CAP_BPF when unprivileged_bpf_disabled=0 (a supported default), so any unprivileged local user can reach it.\nUI:N - The attacker loads and runs their own program; no victim action is required.\nS:U - Impact is confined to the kernel's own security authority — standard local privilege escalation, no crossing into a separate VM/IOMMU boundary.\nC:H - The verifier can be made to believe a register holds a wrong value, allowing a verified-as-safe out-of-bounds read primitive over kernel memory, yielding arbitrary kernel memory disclosure.\nI:H - The same false-bounds primitive enables an out-of-bounds write the verifier \"proved\" safe, giving an arbitrary kernel write usable for privilege escalation and code-flow hijacking.\nA:H - The resulting out-of-bounds accesses on attacker-controlled values readily corrupt kernel memory and panic/crash the system."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:28:47.803Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.12.75"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.18.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.19.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-45933","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:18:26.156628Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-682","lang":"en","type":"CWE","description":"CWE-682 Incorrect Calculation"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T19:26:39.760Z"}}]}}}