Linux Kernel Heap Out-of-Bounds Write Vulnerability
Linux Kernel contains a heap out-of-bounds write vulnerability that could allow an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space.
- Vendor
- Linux
- Product
- Kernel
- CVSS
- 8.3
- EPSS (exploit probability)
- 78.7%
- Status
- kev
- CISA patch-by (BOD 22-01)
- Added to KEV
Is CVE-2021-22555 being exploited?
Yes. CISA added CVE-2021-22555 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 78.7% (scored October 14, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-10-19. Full cross-catalog view: /kev-comparison
What to do
CISA required actionApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
US federal civilian agencies must remediate by (21 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
Other Linux Kernel CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2026-53266 Linux Kernel Out-of-Bounds Write Vulnerabilitywrite-up | [ HIGH ] | 8.8 | 0.8% | |
| CVE-2025-39964 Linux Kernel Race Condition Vulnerabilitywrite-up | [ HIGH ] | 7.8 | 1.4% | |
| CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerabilitywrite-up | [ CRITICAL ] | 9.8 | 2.9% | |
| CVE-2026-53362 Linux Kernel Unspecified Vulnerability | [ HIGH ] | 7.8 | 0.7% | |
| CVE-2022-0995 Linux Kernel Out-of-Bounds Write Vulnerability | [ HIGH ] | 7.8 | 8.9% | |
| CVE-2026-53264 Linux kernel traffic-control subsystem use-after-free racewrite-up | [ HIGH ] | 7.8 | 0.2% | — |
| CVE-2022-0492 Linux Kernel Improper Authentication Vulnerability | [ HIGH ] | 7.8 | 5.5% | |
| CVE-2026-31431 Linux Kernel Incorrect Resource Transfer Between Spheres Vulnerability | [ HIGH ] | 7.8 | 3.4% |