CVE-2021-27771Network attack vector

File upload and directory deletion via SID tampering

Published May 12, 2022 · Updated Sep 17, 2024

File transfer flaws in HCL Sametime 11.6 allow remote authenticated users to upload arbitrary files or delete directories by modifying a SID. The Proxy/Web Chat file-transfer flow consumes a user-modifiable SID cookie for transfers, allowing the altered value to select an unintended upload or directory path. A valid chat session and user interaction are required; exploitation writes a file or deletes directories, potentially interrupting the service.

CVSS severity8.2
High
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

File transfer flaws in HCL Sametime 11.6 allow remote authenticated users to upload arbitrary files or delete directories by modifying a SID. The Proxy/Web Chat file-transfer flow consumes a user-modifiable SID cookie for transfers, allowing the altered value to select an unintended upload or directory path. A valid chat session and user interaction are required; exploitation writes a file or deletes directories, potentially interrupting the service.

The record

CVE
CVE-2021-27771
Published
May 12, 2022
Updated
Sep 17, 2024
Vendor
HCL Software
Product
HCL Sametime
Classifications
CWE-22, CWE-434, T1485
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 12, 2022CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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

6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
7.6NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
8.2HCL SoftwareCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:H

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-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-434Unrestricted Upload of File with Dangerous Type
T1485Data Destruction

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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