In the Linux kernel, the following vulnerability has been resolved: bpf: Preserve id of register in sync_linked_regs() sync_linked_regs() copies the id of known_reg to reg when propagating bounds of known_reg to reg using the off of known_reg, but when known_reg was linked to reg like: known_reg = reg ; both known_reg and reg get same id known_reg += 4 ; known_reg gets off = 4, and its id gets BPF_ADD_CONST now when a call to sync_linked_regs() happens, let's say with the following: if known_reg >= 10 goto pc+2 known_reg's new bounds are propagated to reg but now reg gets BPF_ADD_CONST from the copy
Why It Matters
Analysis dossierWhy It Matters
In the Linux kernel, the following vulnerability has been resolved: bpf: Preserve id of register in sync_linked_regs() sync_linked_regs() copies the id of known_reg to reg when propagating bounds of known_reg to reg using the off of known_reg, but when known_reg was linked to reg like: known_reg = reg ; both known_reg and reg get same id known_reg += 4 ; known_reg gets off = 4, and its id gets BPF_ADD_CONST now when a call to sync_linked_regs() happens, let's say with the following: if known_reg >= 10 goto pc+2 known_reg's new bounds are propagated to reg but now reg gets BPF_ADD_CONST from the copy. This means if another link to reg is created like: another_reg = reg ; another_reg should get the id of reg but assign_scalar_id_before_mov() sees BPF_ADD_CONST on reg and assigns a new id to it. As reg has a new id now, known_reg's link to reg is broken. If we find new bounds for known_reg, they will not be propagated to reg. This can be seen in the selftest added in the next commit: 0: (85) call bpf_get_prandom_u32#7 ; R0=scalar() 1: (57) r0 &= 255 ; R0=scalar(smin=smin32=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff)) 2: (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)) 3: (07) r1 += 4 ; R1=scalar(id=1+4,smin=umin=smin32=umin32=4,smax=umax=smax32=umax32=259,var_off=(0x0; 0x1ff)) 4: (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)) 5: (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) 6: (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)) 7: (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)) 8: (37) r0 /= 0 div by zero When 4 is verified, r1's bounds are propagated to r0 but r0 also gets BPF_ADD_CONST (bug). When 5 is verified, r0 gets a new id (2) and its link with r1 is broken. After 6 we know r1 has bounds [14, 259] and therefore r0 should have bounds [10, 255], therefore the branch at 7 is always taken. But because r0's id was changed to 2, r1's new bounds are not propagated to r0. The verifier still thinks r0 has bounds [6, 255] before 7 and execution can reach div by zero. Fix this by preserving id in sync_linked_regs() like off and subreg_def.
High
Unknown
Unknown
Risk basis: SOC ecosystem technology relevance; HIGH severity; No confirmed exploitation signal in current enrichment
Affected Products & Remediation
1 source-backed product- linux linux kernel · >= 6.11 < 6.12.75; >= 6.13 < 6.18.14; >= 6.19 < 6.19.4 · NVD CPE · Source
Vendor or catalog guidance (source)
Not provided by source
Known exploitation (source facts)
Only what a source states. Unknown means no source has said either way; it is not "not exploited".
- CISA KEV
- Unknown
- Exploited (source statement)
- Unknown
- Publicly disclosed (source)
- Unknown
Suggested hunting (rule-based inference)
SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.
Matched local-privilege-escalation (CVSS AV:L, CVSS PR:L)
Exposure
- Identify hosts reporting this CVE, prioritising shared or multi-user systems.Telemetry: DeviceTvmSoftwareVulnerabilities · A local, low-privilege vector matters most where untrusted users can run code. · Rule local-privilege-escalation
Exploitation evidence
- Look for low-privileged processes spawning SYSTEM or root-level child processes on affected hosts.Telemetry: DeviceProcessEvents · Hunting hypothesis from the CVSS vector; privilege transitions are a focused starting point, not evidence of attack. · Rule local-privilege-escalation
Response
- Confirm the source-stated update on affected hosts.Telemetry: DeviceTvmSoftwareVulnerabilities · Host inventory can verify remediation. · Rule local-privilege-escalation
CISA KEV Record
CISA KEV status was not determined for this record.
Change History & Source Data
— No recorded material change
- CNA / source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
- Record status · verification
- UPDATED · NVD API
- CPE
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Evidence & Provenance
Linked by the query's stored exact CVE association. Review required tables and validation status before use.
DeviceTvmSoftwareVulnerabilities| where CveId == "CVE-2026-45933"| project DeviceId, DeviceName, OSPlatform, OSVersion, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, RecommendedSecurityUpdateId| sort by VulnerabilitySeverityLevel descCorrelated briefings
— No published briefing references this CVE