How severe is CVE-2021-27771?

CVE-2021-27771 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability high.

Is CVE-2021-27771 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27771?

CVE-2021-27771 affects Hcltech Sametime. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27771?

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-2021-27771 published?

CVE-2021-27771 was published on 2022-05-12 and last updated on 2026-06-17.

CVE-2021-27771

CVE-2021-27771 is a high-severity vulnerability in Hcltech Sametime with a CVSS 3.x base score of 8.2. 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-434.

Key facts

Severity: High (CVSS 3.x base score 8.2)
CVSS v2: 6.5
EPSS exploit prediction: 1% (48th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-434
Affected product: Hcltech Sametime
Published: 2022-05-12
Last modified: 2026-06-17

Description

User SID can be modified resulting in an Arbitrary File Upload or deletion of directories causing a Denial of Service. When interacting in a normal matter with the Sametime chat application, users hold a cookie containing their session ID (SID). This value is also used when sending chat messages, receiving notifications and/or transferring files.

Frequently asked questions

What is CVE-2021-27771?: User SID can be modified resulting in an Arbitrary File Upload or deletion of directories causing a Denial of Service. When interacting in a normal matter with the Sametime chat application, users hold a cookie containing their session ID (SID). This value is also used when sending chat messages, receiving notifications and/or transferring files.
How severe is CVE-2021-27771?: CVE-2021-27771 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability high.
Is CVE-2021-27771 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27771?: CVE-2021-27771 affects Hcltech Sametime. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27771?: 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-2021-27771 published?: CVE-2021-27771 was published on 2022-05-12 and last updated on 2026-06-17.

References

https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0097430

Affected products (1)

cpe:2.3:a:hcltech:sametime:11.6:*:*:*:*:*:*:*

More vulnerabilities in Hcltech Sametime

CVE-2021-27772 — High (CVSS 7.1): Users are able to read group conversations without actively taking part in them. Next to one to one conversations,…
CVE-2021-27770 — Medium (CVSS 6.8): The vulnerability was discovered within the “FaviconService”. The service takes a base64-encoded URL which is then…
CVE-2022-42446 — Medium (CVSS 6.5): Starting with Sametime 12, anonymous users are enabled by default. After logging in as an anonymous user, one has the…
CVE-2023-50349 — Medium (CVSS 5.9): Sametime is impacted by a Cross Site Request Forgery (CSRF) vulnerability. Some REST APIs in the Sametime Proxy…
CVE-2024-30122 — Medium (CVSS 5.8): HCL Sametime is impacted by misconfigured security related HTTP headers. It was identified that some HTTP headers were…
CVE-2021-27769 — Medium (CVSS 5.3): Information leakage occurs when a website reveals information that could aid an attacker to further exploit the system.…

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