PatchTheCVECVE-2021-36357: An issue was discovered in OpenPOWER 2.6 firmware
CVE-2021-36357 is a critical-severity flaw (CVSS 9.8) affecting skiboot. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
An issue was discovered in OpenPOWER 2.6 firmware. unpack_timestamp() calls le32_to_cpu() for endian conversion of a uint16_t "year" value, resulting in a type mismatch that can truncate a higher integer value to a smaller one, and bypass a timestamp check. The fix is to use the right endian conversion function.
Why this priority
- Critical severity
- Remotely exploitable, no login, no user action
No fix is published yet: follow the downgrade or mitigation steps.
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 32%) |
| CISA exploited list | No |
| Weakness | CWE-681 |
| Published | 2021-10-22 |
| 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-2021-36357?
skiboot: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2021-36357 being exploited?
CVE-2021-36357 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-2021-36357 affect?
CVE-2021-36357 affects skiboot. Severity is critical (CVSS 9.8). An issue was discovered in OpenPOWER 2.6 firmware. unpack_timestamp() calls le32_to_cpu() for endian conversion of a uint16_t "year" value, resulting in a type mismatch that can truncate a higher integer value to a smaller one, and bypass a
How urgent is CVE-2021-36357?
Priority 56/100. Critical severity; Remotely exploitable, no login, no user action