# CVE-2026-68462: bpf: Reject negative const offsets for buffer pointers

> A flaw in the Linux kernel BPF verifier allows negative offsets to bypass bounds checks, potentially enabling privilege escalation or code execution.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-68462, GHSA-r48x-xhw6-jmg8, UBUNTU-CVE-2026-68462

## What is CVE-2026-68462?

CVE-2026-68462 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

bpf: Reject negative const offsets for buffer pointers

The verifier rejects variable offsets for PTR_TO_TP_BUFFER and PTR_TO_BUF
accesses, but it currently accepts a constant negative offset produced by
pointer arithmetic.

Commit 022ac0750883 ("bpf: use reg->var_off instead of reg->off for
pointers") moved constant pointer offsets from reg->off to reg->var_off.
However, __check_buffer_access() continued to check only the instruction
offset. An access with reg->var_off equal to -8 and an instruction offset
of zero therefore passes verification.

For writable raw tracepoints, the access end is also calculated from the
unsigned reg->var_off.value. An eight-byte access starting at -8 wraps
the calculated end to zero, allowing the program to load and attach
without increasing max_tp_access.

After ensuring that reg->var_off is constant, calculate the effective
access start using signed arithmetic and reject it when it is negative.
Use the validated start to calculate the access end for both
PTR_TO_TP_BUFFER and PTR_TO_BUF.

## Which versions are affected by CVE-2026-68462?


## How do I fix CVE-2026-68462?

Apply the vendor's patch.

## Is CVE-2026-68462 being exploited?

There is no known exploitation of CVE-2026-68462 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68462 and fix it if it is affected.

What it is: CVE-2026-68462 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-68462 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-68462/ (Markdown: https://insights.sbomify.com/CVE-2026-68462/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68462
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68462
- OSV: https://osv.dev/vulnerability/CVE-2026-68462

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68462/
Summaries are generated and may contain mistakes; the official description above is the record.