Vulnerability · Published Sep 2, 2026 · Assigned by GitHub_M

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

Critical 9.3

In plain English

A critical-severity security flaw in prevail from vbpf. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities).

Severity (CVSS 4.0)9.3Critical

Exploit odds (30 days)0.5%top 56.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
vbpf	prevail	< 0.2.4

Weakness: CWE-682 · Vector: 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

References

https://github.com/vbpf/prevail/security/advisories/GHSA-65rv-h458-cq99 x_refsource_CONFIRM
https://github.com/vbpf/prevail/commit/de65234f67d2608b54d12571edb585ead224363c x_refsource_MISC
https://github.com/vbpf/prevail/releases/tag/v0.2.4 x_refsource_MISC