CVE-2021-27760 [Medium] | Input Validation Bypass in Hcl Inotes

An issue was discovered in the Sametime chat feature in the Notes 11.0 - 11.0.1 FP4 clients. An authenticated Sametime chat user could cause Remote Code Execution on another chat client by sending a specially formatted message through chat containing Javascript code.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-05-12	0.15%	0.52%	+0.37%
2	2025-05-08	0.15%	0.15%	-0.00%
3	2025-05-07	—	0.15%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-05-12

0.15%

0.52%

+0.37%

2025-05-08

0.15%

-0.00%

2025-05-07

—

0.15%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
4.6	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:L) Some sensitive info could get out, but not a total data dump. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	2.1	2.5	[email protected]
5.5	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	2.1	3.4	[email protected]
6.0	2.0	MEDIUM	`AV:N/AC:M/Au:S/C:P/I:P/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:M) Exploitation needs some favorable conditions, but not exceptional ones. Authentication (AU:S) A single authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	6.8	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

4.6

3.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

2.1

2.5

[email protected]

5.5

3.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

2.1

3.4

[email protected]

6.0

2.0

MEDIUM

AV:N/AC:M/Au:S/C:P/I:P/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:M): Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:S): A single authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

6.8

6.4

[email protected]

Affected software / configurations for CVE-2021-27760

Vendor	Product	Version	Raw CPE
hcltech	hcl_inotes	11.0.0	cpe:2.3:a:hcltech:hcl_inotes:11.0.0:::::::*
hcltech	hcl_inotes	11.0.1	cpe:2.3:a:hcltech:hcl_inotes:11.0.1:-::::::
hcltech	hcl_inotes	11.0.1	cpe:2.3:a:hcltech:hcl_inotes:11.0.1:fixpack1::::::
hcltech	hcl_inotes	11.0.1	cpe:2.3:a:hcltech:hcl_inotes:11.0.1:fixpack2::::::
hcltech	hcl_inotes	11.0.1	cpe:2.3:a:hcltech:hcl_inotes:11.0.1:fixpack3::::::
hcltech	hcl_inotes	11.0.1	cpe:2.3:a:hcltech:hcl_inotes:11.0.1:fixpack4::::::

References for CVE-2021-27760

URL	Tags
https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0097670	Third Party Advisory

URL

CVE-2021-27760 | HCL Notes 11.0 - 11.0.1 FP4 Sametime Embedded chat clients are vulnerable to group chats loading script on restart

Exploit prediction scoring system (EPSS) score for CVE-2021-27760

Common vulnerability scoring system (CVSS) metrics for CVE-2021-27760

Weakness enumeration for CVE-2021-27760

Affected software / configurations for CVE-2021-27760

References for CVE-2021-27760