This CVE is not an isolated bug — it is the fourth known manifestation of a vulnerability family rooted in how BPF's verifier communicates security-critical type information to runtime cleanup passes. The pattern traces back through CVE-2022-1048, CVE-2021-4202, and CVE-2020-27194, each patched conservatively, none resolved structurally. The underlying issue: the BPF verifier tracks pointer/spill metadata as abstract state during verification, but runtime cleanup passes like __clean_func_state() operate on raw stack bytes. When cleanup clears dead stack halves, it cannot distinguish between a pointer spill and a scalar spill — because that knowledge lives in the verifier's interpretation, not in the runtime's data structure. The current fix addresses this by preserving pointer spill slots intact while still allowing cleanup of scalar slots. This corrects the immediate security failure but introduces a new asymmetry: the code now makes security decisions based on metadata it itself may have corrupted in earlier passes. More concerning, the fix encodes an explicit rule ('leave pointer spill slots alone') that didn't exist in the original design, creating new load-bearing assumptions attackers can probe in future optimization passes. The deeper problem is architectural: BPF lacks an enforced contract separating what the verifier knows from what cleanup assumes. Until that separation is made structurally impossible to violate — not policed through special cases — this vulnerability family will continue producing offspring. Treat each CVE in this lineage as evidence that the verifier-to-runtime handoff carries unresolved security debt. Monitor not just whether your kernels are patched, but whether any custom BPF programs, legacy JIT paths, or deprecated syscalls might exercise code paths that predated this fix and remain unpatched.
CVE-2026-72426
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: bpf: Preserve pointer spill metadata during half-slot cleanup __clean_func_state() cleans dead stack slots in 4-byte halves. When the high half of a STACK_SPILL slot is dead and the low half remains live, cleanup converts the live low half to STACK_MISC or STACK_ZERO and clears the saved spilled_ptr metadata. That conversion is safe only for scalar spills. For a pointer spill, this metadata clear lets a later 32-bit fill from the still-live half avoid the normal non-scalar register-fill check and be treated as an ordinary scalar stack read. Leave non-scalar spill slots intact in this half-live shape. This is conservative for pruning and preserves the existing check_stack_read_fixed_off() rejection path for partial fills from pointer spills.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysisA detailed technical summary for this CVE is being prepared.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataThere is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.
Free. We build fixes in the order the community asks for them — and we’ll tell you the moment this one lands.
We develop and verify an original fix where the vendor hasn’t, from $4,900. Deployed to your staging first — never straight to production.
Scope it with usSee what else the community needs solved on the solutions-needed board.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-72426 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesThis CVE is not an isolated bug — it is the fourth known manifestation of a vulnerability family rooted in how BPF's verifier communicates security-critical type information to runtime cleanup passes. The pattern traces back through CVE-2022-1048, CVE-2021-4202, and CVE-2020-27194, each patched conservatively, none resolved structurally. The underlying issue: the BPF verifier tracks pointer/spill metadata as abstract state during verification, but runtime cleanup passes like __clean_func_state() operate on raw stack bytes. When cleanup clears dead stack halves, it cannot distinguish between a pointer spill and a scalar spill — because that knowledge lives in the verifier's interpretation, not in the runtime's data structure. The current fix addresses this by preserving pointer spill slots intact while still allowing cleanup of scalar slots. This corrects the immediate security failure but introduces a new asymmetry: the code now makes security decisions based on metadata it itself may have corrupted in earlier passes. More concerning, the fix encodes an explicit rule ('leave pointer spill slots alone') that didn't exist in the original design, creating new load-bearing assumptions attackers can probe in future optimization passes. The deeper problem is architectural: BPF lacks an enforced contract separating what the verifier knows from what cleanup assumes. Until that separation is made structurally impossible to violate — not policed through special cases — this vulnerability family will continue producing offspring. Treat each CVE in this lineage as evidence that the verifier-to-runtime handoff carries unresolved security debt. Monitor not just whether your kernels are patched, but whether any custom BPF programs, legacy JIT paths, or deprecated syscalls might exercise code paths that predated this fix and remain unpatched.
Practitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-72426 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data