How severe is CVE-2021-27335?

CVE-2021-27335 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-27335 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27335?

CVE-2021-27335 affects Kollectapp Kollect. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27335?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-27335 published?

CVE-2021-27335 was published on 2021-02-18 and last updated on 2026-06-17.

CVE-2021-27335

CVE-2021-27335 is a critical-severity vulnerability in Kollectapp Kollect with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (86th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Kollectapp Kollect
Published: 2021-02-18
Last modified: 2026-06-17

Description

KollectApps before 4.8.16c is affected by insecure Java deserialization, leading to Remote Code Execution via a ysoserial.payloads.CommonsCollections parameter.

Frequently asked questions

What is CVE-2021-27335?: KollectApps before 4.8.16c is affected by insecure Java deserialization, leading to Remote Code Execution via a ysoserial.payloads.CommonsCollections parameter.
How severe is CVE-2021-27335?: CVE-2021-27335 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-27335 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27335?: CVE-2021-27335 affects Kollectapp Kollect. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27335?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-27335 published?: CVE-2021-27335 was published on 2021-02-18 and last updated on 2026-06-17.

References

https://hacked0x90.net/index.php/2021/02/15/kollectapp-insecure-java-deserialization/

Affected products (1)

cpe:2.3:a:kollectapp:kollect:*:*:*:*:*:*:*:*

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