PatchTheCVECVE-2021-27335: KollectApps before 4.8.16c is affected by insecure Java deserialization, leading to Remote Code Execution via
CVE-2021-27335 is a critical-severity flaw (CVSS 9.8) affecting kollect. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
KollectApps before 4.8.16c is affected by insecure Java deserialization, leading to Remote Code Execution via a ysoserial.payloads.CommonsCollections parameter.
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 | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 3.0% (top 13%) |
| CISA exploited list | No |
| Weakness | CWE-502 |
| 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-2021-27335?
kollect: upgrade to 4.8.16c. Exact commands for each OS are on this page.
Is CVE-2021-27335 being exploited?
CVE-2021-27335 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-2021-27335 affect?
CVE-2021-27335 affects kollect. Severity is critical (CVSS 9.8). KollectApps before 4.8.16c is affected by insecure Java deserialization, leading to Remote Code Execution via a ysoserial.payloads.CommonsCollections parameter.
How urgent is CVE-2021-27335?
Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action