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Security Bulletin: Mitigations are being announced to address CVE-2020-4839 and CVE-2021-29695

Security Bulletin


IBM products 8335-GCA, 8335-GTA, and 8335-GTB have identified security vulnerabilities.

Vulnerability Details

CVEID:   CVE-2020-4839
DESCRIPTION:   IBM Host firmware for LC-class Systems is vulnerable to a stack based buffer overflow, caused by improper bounds checking. A remote privileged attacker could exploit this vulnerability and cause a denial of service.
CVSS Base score: 4.9
CVSS Temporal Score: See: for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H)

CVEID:   CVE-2021-29695
DESCRIPTION:   IBM Host firmware for LC-class Systems could allow a remote attacker to traverse directories on the system. An attacker could send a specially-crafted URL request that would allow them to delete arbitrary files on the system.
CVSS Base score: 4.9
CVSS Temporal Score: See: for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N)

Affected Products and Versions

Affected Product(s)Version(s)
8335-GCA, 8335-GTA, and 8335-GTBOP820



Workarounds and Mitigations

Mitigations for these vulnerabilities:
  1. Use strong passwords that are at least 16 characters long with a mixture of upper and lowercase letters, numbers, and special characters. By using more complex passwords, it makes it more difficult for malicious users to discover valid user credentials.
  2. Keep the management network separate from the public network. Keeping the management network separate lessens security exposures by reducing the number of individuals who can access the systems.
  3. Use an account which has the minimum authority needed.  Consider using an operator session for normal operations and using an admin session only when making administrative changes to the BMC.
  4. Limit the duration sessions are logged in.  Always log out of sessions when done using them.  The default web session time out is 10 minutes, and can be changed from the  "Services" web page.
  5. Place the BMC's management network behind a secure Linux box.  This may also be known as a jump box or bastion host.  Then secure that box with high security, multi-factor authentication, with logging and monitoring BMC logs, available from the BMC's web interface.

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This Vulnerability was found by Ye Li and Zhuo Ma From Tencent Security Xuanwu Lab.

Change History

18 May 2021: Initial Publication

*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.


According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.

Document Location


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Document Information

Modified date:
08 September 2021