CVE-2021-27770Network attack vector

Authenticated SSRF via base64-encoded FaviconService URL

Published May 12, 2022 · Updated Sep 16, 2024

Server-side request forgery in HCL Sametime 11.6 allows remote authenticated users to make server-originated requests through FaviconService. FaviconService decodes a client-supplied base64 URL and directs the web server to request it without a published destination restriction. Exploitation requires low-privileged access and user interaction; HCL describes the meetings-function linkage as an assumption, so the exposed route is not confirmed.

CVSS severity6.8
Medium
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Server-side request forgery in HCL Sametime 11.6 allows remote authenticated users to make server-originated requests through FaviconService. FaviconService decodes a client-supplied base64 URL and directs the web server to request it without a published destination restriction. Exploitation requires low-privileged access and user interaction; HCL describes the meetings-function linkage as an assumption, so the exposed route is not confirmed.

The record

CVE
CVE-2021-27770
Published
May 12, 2022
Updated
Sep 16, 2024
Vendor
HCL Software
Product
HCL Sametime
Classifications
CWE-472, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 12, 2022CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=11.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

HCL Software · HCL Sametimeversion=11.6

Published CVSS scores

6.8HCL SoftwareCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:L
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-472External Control of Assumed-Immutable Web Parameter
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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