bpf: backtrack_insn(): Handle ld_{abs,ind} subprog exit edge
Nicholas Carlini reported a bug in precision backtracking mechanism
for BPF_LD | BPF_{IND,ABS} instructions. These instructions are
modelled as two branches:
- fallthrough;
- implicit exit from current subprogram.
The implicit exit case was not handled by the backtrack_insn()
function. When backtracking such a path backtrack_insn() did not
call bt_subprog_enter(), which meant that backtracking continued
manipulating precision marks in a caller frame, while looking at
instructions in a callee frame.
This lead to segmentation faults during verification (see the
selftest), or unsound state pruning.
Metrics
Affected Vendors & Products
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OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.
| Vendors | Products |
|---|---|
|
Linux
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|
Linux Kernel
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|
| Source | ID | Title |
|---|---|---|
 Debian DLA |
DLA-4904-1 | linux-6.12 security update |
 Ubuntu USN |
USN-9019-1 | Linux kernel (Azure) vulnerabilities |
| Ubuntu USN |
USN-9020-1 | Linux kernel vulnerabilities |
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
Wed, 21 Oct 2026 13:15:00 +0000
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| References |
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Thu, 15 Oct 2026 13:30:00 +0000
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Fri, 25 Sep 2026 17:15:00 +0000
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| Weaknesses | CWE-119 |
Fri, 25 Sep 2026 10:30:00 +0000
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| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: backtrack_insn(): Handle ld_{abs,ind} subprog exit edge Nicholas Carlini reported a bug in precision backtracking mechanism for BPF_LD | BPF_{IND,ABS} instructions. These instructions are modelled as two branches: - fallthrough; - implicit exit from current subprogram. The implicit exit case was not handled by the backtrack_insn() function. When backtracking such a path backtrack_insn() did not call bt_subprog_enter(), which meant that backtracking continued manipulating precision marks in a caller frame, while looking at instructions in a callee frame. This lead to segmentation faults during verification (see the selftest), or unsound state pruning. | |
| Title | bpf: backtrack_insn(): Handle ld_{abs,ind} subprog exit edge | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-21T12:54:27.055Z
Reserved: 2026-09-25T10:19:56.075Z
Link: CVE-2026-98085
Vulnrichment
No data.
NVD
Status : Undergoing Analysis
Published: 2026-09-25T11:17:38.087
Modified: 2026-10-21T13:21:22.137
Link: CVE-2026-98085
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-26T13:00:14Z