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CRITICAL severity

Off-by-one Error in v2fly/v2ray-coreGHSA-4cxw-hq44-r344

CRITICALFix: v2fly/v2ray-core@c1af2bf

GHSA-4cxw-hq44-r344 is a critical-severity (CVSS 9.1) CWE-193 vulnerability in github.com/v2fly/v2ray-core/v4. A fix is available for github.com/v2fly/v2ray-core/v4 — see the affected versions and patch details below.

Also known asCVE-2021-4070GO-2022-0550
Published
Updated
Affected
2 pkgs
Patched
1 / 2
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs57th percentile — riskier than 57% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-4cxw-hq44-r344 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected
🐹github.com/v2fly/v2ray-core/v4🐹github.com/v2fly/v2ray-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

v2fly/v2ray-core prior to 4.44.0 is vulnerable to an off-by-one error. Indexing operations on arrays, slices, or strings should use an index at most one less than the length. If the index is checked for being less than or equal to the length (<=), instead of less than the length (<), the index could be out of bounds.

Affected Packages

2 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/v2fly/v2ray-core/v4all versions4.44.0go get github.com/v2fly/v2ray-core/v4@v4.44.0
🐹Gogithub.com/v2fly/v2ray-coreall versionsNo fix

Affected Products

1 product · 1 configurations
Application
v2ray-corev2fly
< 4.44.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/v2fly/v2ray-core/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/v2fly/v2ray-core/v4 to 4.44.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4cxw-hq44-r344 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

v2fly/v2ray-core prior to 4.44.0 is vulnerable to an off-by-one error. Indexing operations on arrays, slices, or strings should use an index at most one less than the length. If the index is checked for being less than or equal to the length (`<=`), instead of less than the length (`<`), the index could be out of bounds.
O3 Security · Impact-Aware SCA

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Off-by-one Error in v2fly/v2ray-core (Critical 9.1)