PatchTheCVECVE-2021-4070: Off-by-one Error in GitHub repository v2fly/v2ray-core prior to 4.44.0.
CVE-2021-4070 is a critical-severity flaw (CVSS 9.1) affecting v2ray-core. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Off-by-one Error in GitHub repository v2fly/v2ray-core prior to 4.44.0.
Why this priority
- Critical severity
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.1 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.9% (top 42%) |
| CISA exploited list | No |
| Weakness | CWE-193 |
| Published | 2022-02-23 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-4070?
v2ray-core: upgrade to 4.44.0. Exact commands for each OS are on this page.
Is CVE-2021-4070 being exploited?
CVE-2021-4070 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-4070 affect?
CVE-2021-4070 affects v2ray-core. Severity is critical (CVSS 9.1). Off-by-one Error in GitHub repository v2fly/v2ray-core prior to 4.44.0.
How urgent is CVE-2021-4070?
Priority 56/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action