Security readout for executives and security teams
Plain-English summary
HCL Sametime 11.6 has a FaviconService issue that can make the Sametime server request an attacker-controlled URL. Business risk is moderate: a misused collaboration server could expose sensitive internal resources or create limited integrity and availability impact.
Executive priority
Treat as a scheduled but visible remediation item. Prioritize internet-facing or broadly accessible Sametime systems because server-side requests may reach resources users normally cannot access directly.
Technical view
The issue is in FaviconService, which accepts a base64-encoded URL and has the webserver request it. The CVSS 3.1 score is 6.8 with network attack vector, low complexity, low privileges, user interaction, high confidentiality impact, and low integrity and availability impact.
Likely exposure
Exposure is limited to HCL Sametime 11.6 per the source bundle. Deployments using meeting functionality or exposing the affected service to authenticated users are the most relevant candidates for review.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. The CVSS vector indicates exploitation requires low privileges and user interaction, so this is not described as unauthenticated remote compromise.
Researcher notes
Evidence is sparse beyond the CVE description, CVSS vector, affected version, and HCL advisory reference. Do not assume affected versions beyond 11.6 or specific fixes unless confirmed in HCL guidance.
Mitigation direction
- Review HCL KB0097430 for the vendor-approved fix or workaround.
- Inventory all HCL Sametime 11.6 instances.
- Apply HCL-provided updates or configuration changes when identified.
- Limit outbound server egress to required destinations where feasible.
- Monitor Sametime servers for unusual outbound HTTP requests.
Validation and detection
- Confirm whether HCL Sametime 11.6 is deployed.
- Check Sametime patch level against HCL KB0097430 guidance.
- Review exposure of FaviconService and meeting-related URL handling.
- Inspect server logs for unexpected outbound requests from Sametime.
- Document compensating controls if vendor remediation is pending.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-472: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-27770 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:L2.14.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.8MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0097430CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
External Control of Assumed-Immutable Web Parameter
External Control of Assumed-Immutable Web Parameter represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.