# CVE-2026-53671: PREVAIL: Context-write no-op in do_mem_store allows unsafe eBPF programs to pass verification

> A flaw in the PREVAIL eBPF verifier allows unsafe programs to bypass checks, potentially enabling arbitrary code execution or privilege escalation.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Sep 2026
- **Updated:** 5 Sep 2026
- **Also known as:** GHSA-65rv-h458-cq99

## What is CVE-2026-53671?

CVE-2026-53671 is a critical vulnerability in vbpf prevail, published on 2 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

PREVAIL is a Polynomial-Runtime EBPF Verifier using an Abstract Interpretation Layer. Prior to version 0.2.4, the abstract transformer in prevail treats writes through a T_CTX-typed base register as a silent no-op: do_mem_store in src/crab/ebpf_transformer.cpp only models T_STACK stores, and the checker's T_CTX bounds arm never tests AccessType::write. An attacker can craft an eBPF program that overwrites a context field (e.g., ctx->data), reload that field typed as T_PACKET, and dereference an attacker-controlled address — and prevail will report the program as safe. This issue has been patched in version 0.2.4.

Weakness: CWE-682 (Incorrect Calculation)

## Which versions are affected by CVE-2026-53671?


## How do I fix CVE-2026-53671?

No fix has been published for CVE-2026-53671 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-53671 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53671 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53671 and fix it if it is affected.

What it is: CVE-2026-53671 is a critical vulnerability in vbpf prevail, published on 2 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53671 exists.

Affected product: vbpf prevail. 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-2026-53671/ (Markdown: https://insights.sbomify.com/CVE-2026-53671/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53671
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53671
- OSV: https://osv.dev/vulnerability/CVE-2026-53671

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53671/
Summaries are generated and may contain mistakes; the official description above is the record.