CVE-2026-53671
Received Received - Intake

eBPF Context Field Write Bypass in PREVAIL

Publication date: 2026-09-02

Last updated on: 2026-09-02

Assigner: GitHub, Inc.

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.

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Meta Information

Published
2026-09-02
Last Modified
2026-09-02
Generated
2026-09-03
AI Q&A
2026-09-02
EPSS Evaluated
N/A
NVD
CVE-2026-53671
EUVD
EUVD-2026-70243

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
vbpf prevail to 0.2.4 (exc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-682 The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.

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Executive Summary

CVE-2026-53671 is a vulnerability in PREVAIL, an eBPF verifier. It allows attackers to craft malicious eBPF programs that bypass verification by overwriting read-only context fields like ctx->data. The verifier incorrectly treated these writes as harmless, enabling further exploitation such as dereferencing attacker-controlled memory addresses.

Detection Guidance

To detect this vulnerability, check if you are running PREVAIL versions prior to 0.2.4. Inspect eBPF programs for writes to context pointer fields like ctx->data, ctx->data_end, or ctx->meta. Use static analysis tools to verify verifier behavior against the patched version.

Impact Analysis

This vulnerability could allow an attacker to execute arbitrary code or cause memory corruption in systems using PREVAIL versions before 0.2.4. It may lead to out-of-bounds memory access, information disclosure, or denial of service in affected environments.

Compliance Impact

This vulnerability could potentially lead to information disclosure or memory corruption, which may violate data protection requirements under GDPR (e.g., unauthorized access to personal data) and HIPAA (e.g., exposure of protected health information). The ability to bypass verification and manipulate memory could result in unauthorized data access or modification, undermining compliance with these regulations.

Mitigation Strategies

Upgrade PREVAIL to version 0.2.4 or later immediately. Review and update eBPF programs to ensure no writes target read-only context fields. Apply additional sandboxing or verification layers for eBPF programs to prevent exploitation.

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