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Security Bulletin: Vulnerability in gencore affects AIX (CVE-2020-4887)

Security Bulletin


There is a vulnerability in the gencore user command that affects AIX.

Vulnerability Details

CVEID:   CVE-2020-4887
DESCRIPTION:   IBM AIX could allow a local user to exploit a vulnerability in the gencore user command to create arbitrary files in any directory.
CVSS Base score: 6.2
CVSS Temporal Score: See: for the current score.
CVSS Vector: (CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N)

Affected Products and Versions

Affected Product(s) Version(s)
AIX 7.1
AIX 7.2
VIOS 3.1
The vulnerabilities in the following filesets are being addressed:
Fileset Lower Level Upper Level
To find out whether the affected filesets are installed on your systems, refer to the lslpp command found in AIX user's guide.
Example:  lslpp -L | grep -i bos.mp64



IBM has assigned the following APARs to this problem:

7.1.5 IJ28825 SP08
7.2.3 IJ28826 SP07
7.2.4 IJ28827 SP04
7.2.5 IJ28828 SP02

3.1.0 IJ28826
3.1.1 IJ28827
3.1.2 IJ28828
Subscribe to the APARs here:
By subscribing, you will receive periodic email alerting you to the status of the APAR, and a link to download the fix once it becomes available.
AIX and VIOS fixes are available.
An LPAR system reboot is required to complete the iFix installation, or Live Update may be used on AIX 7.2 to avoid a reboot.
The AIX and VIOS fixes can be downloaded via ftp or http from:
The link above is to a tar file containing this signed advisory, fix packages, and OpenSSL signatures for each package. The fixes below include prerequisite checking. This will enforce the correct mapping between the fixes and AIX Technology Levels.
AIX Level Interim Fix (*.Z) IJ28825m5a.201221.epkg.Z IJ28825m5b.201221.epkg.Z IJ28825m6a.201221.epkg.Z IJ28825m6b.201221.epkg.Z IJ28825m6c.201221.epkg.Z IJ28825m7a.201221.epkg.Z IJ28825m7b.201221.epkg.Z IJ28826m3a.201221.epkg.Z IJ28826m4a.201221.epkg.Z IJ28826m5a.201221.epkg.Z IJ28827m0a.201222.epkg.Z IJ28827m1a.201222.epkg.Z IJ28827m2a.201222.epkg.Z IJ28827m2b.201222.epkg.Z IJ28827m2c.201222.epkg.Z IJ28827m3a.210306.epkg.Z IJ28828m1a.201222.epkg.Z IJ28828m1a.201222.epkg.Z
Please note that the above table refers to AIX TL/SP level as opposed to fileset level, i.e., is AIX 7200-03-05.
NOTE:  Multiple iFixes are provided for AIX 7100-05-05, 7100-05-06, 7100-05-07, and 7200-04-02.
IJ28825m5a is for AIX 7100-05-05 with bos.mp64 fileset level
IJ28825m5b is for AIX 7100-05-05 with bos.mp64 fileset level
IJ28825m6a is for AIX 7100-05-06 with bos.mp64 fileset level
IJ28825m6b is for AIX 7100-05-06 with bos.mp64 fileset level
IJ28825m6c is for AIX 7100-05-06 with bos.mp64 fileset level
IJ28825m7a is for AIX 7100-05-07 with bos.mp64 fileset level
IJ28825m7b is for AIX 7100-05-07 with bos.mp64 fileset level
IJ28827m2a is for AIX 7200-04-02 with bos.mp64 fileset level 
IJ28827m2b is for AIX 7200-04-02 with bos.mp64 fileset level
IJ28827m2c is for AIX 7200-04-02 with bos.mp64 fileset level
Please reference the Affected Products and Version section above for help with checking installed fileset levels.
VIOS Level Interim Fix (*.Z) IJ28826m3a.201221.epkg.Z IJ28826m4a.201221.epkg.Z IJ28826m5a.201221.epkg.Z IJ28827m0a.201222.epkg.Z IJ28827m1b.201222.epkg.Z IJ28827m2c.201222.epkg.Z IJ28827m2b.201222.epkg.Z IJ28827m2a.201222.epkg.Z IJ28827m3a.210306.epkg.Z IJ28828m1a.201222.epkg.Z IJ28828m1a.201222.epkg.Z
The fixes are cumulative and address previously issued AIX/VIOS kernel security bulletins with respect to SP and TL, which includes:
To extract the fixes from the tar file:
tar xvf gencore_fix.tar
cd gencore_fix
Verify you have retrieved the fixes intact:
The checksums below were generated using the "openssl dgst -sha256 [filename]" command as the following:
openssl dgst -sha256 filename
6d8482ef0decc18eb9cb37820ba1b8099cdf158523b6a95006cee1a081a48f83 IJ28825m5a.201221.epkg.Z
343e07de2e256b5439851da18ba3ea3a21dca3a98b55cba09306d46145c952de IJ28825m5b.201221.epkg.Z
71c903ff543d5c583d74330a48fdd60ab52d82ff8214407237ca9b8929d38d27 IJ28825m6a.201221.epkg.Z
e2798e2d78872870e153fad899b7f9b4c0eb0447b1068211050a91230989aa71 IJ28825m6b.201221.epkg.Z
3ac89e2e382cba3c440f37789f437a48be61f2bebcdf398e0a97ab2fa5dd20f7 IJ28825m6c.201221.epkg.Z
6bd374a44b0d571ce6628afb0ea163df493f942ddd618a616be24fa1839d7845 IJ28825m7a.201221.epkg.Z
0bce6ede7a2ea902d614eb892af533d90b4dfedf3a1d05f17b7ec1c21782fc38 IJ28825m7b.201221.epkg.Z
ec4f01c8bc31b61f9679be6d03d3ed7ac9713a4349b31c855eaf4b0f4b9cf377 IJ28826m3a.201221.epkg.Z
a3dae1d428ea866a7dab943285a4ebef8fa420451bd23bfeba919761fb4cd300 IJ28826m4a.201221.epkg.Z
8c6bb8caf628078c0387433ff978067280477d0b3ea3568102096cbf005a633c IJ28826m5a.201221.epkg.Z
5c9ad296cecb576dcef4631b75fa1987a9c856de07e466a5e1a6aa8529b7269f IJ28827m0a.201222.epkg.Z
8911ccd41e8926d247de9abc9da7387c1158a4b7606a945b2659dfaa95a6c8f6 IJ28827m1a.201222.epkg.Z
e6b977bef6e2d799b5b0ad0fd0a03c3b59922ee0a76ccaf414db97ca879e1329 IJ28827m1b.201222.epkg.Z
0637ffbb60a918da32548c3861fbfa381db04be375cf21d372efdef3711ca569 IJ28827m2a.201222.epkg.Z
50786a721811b2eff98fbb24c85ed9bb8977f44891d29114d8fe43d79c0fe10e IJ28827m2b.201222.epkg.Z
4c6b71538dedded55aeffe7451a02998885dcc80ca12b1fa7937d53ff1a26402 IJ28827m2c.201222.epkg.Z
321cd8cf7362d25c05948b0717029e54bcc7233002a5eaae1b30d5e88d5b5f13 IJ28827m3a.210306.epkg.Z
d8e107386c7eb45966ef9f3635f4e7253665c04795427f06a7e73a55b8847a54 IJ28828m1a.201222.epkg.Z
These sums should match exactly. The OpenSSL signatures in the tar file and on this advisory can also be used to verify the integrity of the fixes. If the sums or signatures cannot be confirmed, contact IBM Support at and describe the discrepancy.        
openssl dgst -sha1 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file]
openssl dgst -sha1 -verify [pubkey_file] -signature [ifix_file].sig [ifix_file]
Published advisory OpenSSL signature file location:
An LPAR system reboot is required to complete the iFix installation, or Live Update may be used on AIX 7.2 to avoid a reboot.
If possible, it is recommended that a mksysb backup of the system be created. Verify it is both bootable and readable before proceeding.
To preview a fix installation:
installp -a -d fix_name -p all  # where fix_name is the name of the
                                            # fix package being previewed.
To install a fix package:
installp -a -d fix_name -X all  # where fix_name is the name of the
                                            # fix package being installed.
Interim fixes have had limited functional and regression testing but not the full regression testing that takes place for Service Packs; however, IBM does fully support them.
Interim fix management documentation can be found at:
To preview an interim fix installation:
emgr -e ipkg_name -p         # where ipkg_name is the name of the
                                         # interim fix package being previewed.
To install an interim fix package:
emgr -e ipkg_name -X         # where ipkg_name is the name of the
                                         # interim fix package being installed.

Workarounds and Mitigations


Get Notified about Future Security Bulletins



Change History

19 Jan 2021: Initial Publication
30 March 2021: iFix now provided for AIX 7200-04-03 and VIOS

*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:
30 March 2021