How severe is CVE-2021-27899?

CVE-2021-27899 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-27899 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27899?

CVE-2021-27899 primarily affects Proofpoint Insider Threat Management. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-27899?

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

When was CVE-2021-27899 published?

CVE-2021-27899 was published on 2021-04-06 and last updated on 2026-06-17.

CVE-2021-27899

CVE-2021-27899 is a high-severity vulnerability in Proofpoint Insider Threat Management with a CVSS 3.x base score of 7.4. 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-295.

Key facts

Severity: High (CVSS 3.x base score 7.4)
CVSS v2: 5.8
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Proofpoint Insider Threat Management
Published: 2021-04-06
Last modified: 2026-06-17

Description

The Proofpoint Insider Threat Management Agents (formerly ObserveIT Agent) for MacOS and Linux perform improper validation of the ITM Server's certificate, which enables a remote attacker to intercept and alter these communications using a man-in-the-middle attack. All versions before 7.11.1 are affected. Agents for Windows and Cloud are not affected.

Frequently asked questions

What is CVE-2021-27899?: The Proofpoint Insider Threat Management Agents (formerly ObserveIT Agent) for MacOS and Linux perform improper validation of the ITM Server's certificate, which enables a remote attacker to intercept and alter these communications using a man-in-the-middle attack. All versions before 7.11.1 are affected. Agents for Windows and Cloud are not affected.
How severe is CVE-2021-27899?: CVE-2021-27899 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-27899 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27899?: CVE-2021-27899 primarily affects Proofpoint Insider Threat Management. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-27899?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-27899 published?: CVE-2021-27899 was published on 2021-04-06 and last updated on 2026-06-17.

References

https://www.proofpoint.com/us/security/security-advisories/pfpt-sa-2021-0004

Affected products (2)

cpe:2.3:a:proofpoint:insider_threat_management:*:*:*:*:*:linux:*:*
cpe:2.3:a:proofpoint:insider_threat_management:*:*:*:*:*:macos:*:*

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