CVE-2026-43070
CVE-2026-43070 is a high-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-125.
Key facts
- Severity: High (CVSS 3.x base score 7.8)
- EPSS exploit prediction: 0% (2nd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-27373
- Weakness: CWE-125
- Affected product: Linux Linux Kernel
- Published:
- Last modified:
Description
In the Linux kernel, the following vulnerability has been resolved: bpf: Reset register ID for BPF_END value tracking When a register undergoes a BPF_END (byte swap) operation, its scalar value is mutated in-place. If this register previously shared a scalar ID with another register (e.g., after an `r1 = r0` assignment), this tie must be broken. Currently, the verifier misses resetting `dst_reg->id` to 0 for BPF_END. Consequently, if a conditional jump checks the swapped register, the verifier incorrectly propagates the learned bounds to the linked register, leading to false confidence in the linked register's value and potentially allowing out-of-bounds memory accesses. Fix this by explicitly resetting `dst_reg->id` to 0 in the BPF_END case to break the scalar tie, similar to how BPF_NEG handles it via `__mark_reg_known`.
Frequently asked questions
- What is CVE-2026-43070?
- In the Linux kernel, the following vulnerability has been resolved: bpf: Reset register ID for BPF_END value tracking When a register undergoes a BPF_END (byte swap) operation, its scalar value is mutated in-place. If this register previously shared a scalar ID with another register (e.g., after an `r1 = r0` assignment), this tie must be broken. Currently, the verifier misses resetting `dst_reg->id` to 0 for BPF_END. Consequently, if a conditional jump checks the swapped register, the verifier incorrectly propagates the learned bounds to the linked register, leading to false confidence in the linked register's value and potentially allowing out-of-bounds memory accesses. Fix this by explicitly resetting `dst_reg->id` to 0 in the BPF_END case to break the scalar tie, similar to how BPF_NEG handles it via `__mark_reg_known`.
- How severe is CVE-2026-43070?
- CVE-2026-43070 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-43070 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-43070?
- CVE-2026-43070 primarily affects Linux Linux Kernel. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2026-43070?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-43070 have an EU (EUVD) identifier?
- Yes. CVE-2026-43070 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-27373.
- When was CVE-2026-43070 published?
- CVE-2026-43070 was published on 2026-05-05 and last updated on 2026-06-17.
References
- https://git.kernel.org/stable/c/0d15c3611a2cc5d08993545d4032055ae10ae2c1
- https://git.kernel.org/stable/c/a17443af874229408ce6b78e2c8a2b5adeb4b7d8
- https://git.kernel.org/stable/c/a3125bc01884431d30d731461634c8295b6f0529
Affected products (5)
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*
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