PatchTheCVECVE-2021-27378: An issue was discovered in the rand_core crate before 0.6.2 for Rust
CVE-2021-27378 is a critical-severity flaw (CVSS 9.8) affecting rand core. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
An issue was discovered in the rand_core crate before 0.6.2 for Rust. Because read_u32_into and read_u64_into mishandle certain buffer-length checks, a random number generator may be seeded with too little data.
Why this priority
- Critical severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.2% (top 31%) |
| CISA exploited list | No |
| Weakness | CWE-131 |
| Published | 2021-02-18 |
| 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-2021-27378?
rand core: upgrade to 0.6.2. Exact commands for each OS are on this page.
Is CVE-2021-27378 being exploited?
CVE-2021-27378 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-2021-27378 affect?
CVE-2021-27378 affects rand core. Severity is critical (CVSS 9.8). An issue was discovered in the rand_core crate before 0.6.2 for Rust. Because read_u32_into and read_u64_into mishandle certain buffer-length checks, a random number generator may be seeded with too little data.
How urgent is CVE-2021-27378?
Priority 57/100. Critical severity; Remotely exploitable, no login, no user action