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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2020.2686 USN-4432-2: GRUB2 regression 6 August 2020 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: GRUB2 Publisher: Ubuntu Operating System: Ubuntu Impact/Access: Denial of Service -- Unknown/Unspecified Resolution: Patch/Upgrade Original Bulletin: https://usn.ubuntu.com/4432-2/ Comment: Fixes regressions introduced in USN-4432-1 which lead to boot failures - --------------------------BEGIN INCLUDED TEXT-------------------- USN-4432-2: GRUB2 regression 04 August 2020 USN-4432-1 introduced a regression in the GRUB2 bootloader. Releases o Ubuntu 20.04 LTS o Ubuntu 18.04 LTS o Ubuntu 16.04 LTS o Ubuntu 14.04 ESM Packages o grub2 - GRand Unified Bootloader o grub2-signed - GRand Unified Bootloader Details USN-4432-1 fixed vulnerabilities in GRUB2 affecting Secure Boot environments. Unfortunately, the update introduced regressions for some BIOS systems (either pre-UEFI or UEFI configured in Legacy mode), preventing them from successfully booting. This update addresses the issue. Users with BIOS systems that installed GRUB2 versions from USN-4432-1 should verify that their GRUB2 installation has a correct understanding of their boot device location and installed the boot loader correctly. We apologize for the inconvenience. Original advisory details: Jesse Michael and Mickey Shkatov discovered that the configuration parser in GRUB2 did not properly exit when errors were discovered, resulting in heap-based buffer overflows. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-10713) Chris Coulson discovered that the GRUB2 function handling code did not properly handle a function being redefined, leading to a use-after-free vulnerability. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-15706) Chris Coulson discovered that multiple integer overflows existed in GRUB2 when handling certain filesystems or font files, leading to heap-based buffer overflows. A local attacker could use these to execute arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-14309, CVE-2020-14310, CVE-2020-14311) It was discovered that the memory allocator for GRUB2 did not validate allocation size, resulting in multiple integer overflows and heap-based buffer overflows when handling certain filesystems, PNG images or disk metadata. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-14308) Mathieu Trudel-Lapierre discovered that in certain situations, GRUB2 failed to validate kernel signatures. A local attacker could use this to bypass Secure Boot restrictions. (CVE-2020-15705) Colin Watson and Chris Coulson discovered that an integer overflow existed in GRUB2 when handling the initrd command, leading to a heap-based buffer overflow. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-15707) Update instructions The problem can be corrected by updating your system to the following package versions: Ubuntu 20.04 o grub-efi-amd64-bin - 2.04-1ubuntu26.2 o grub-efi-amd64-signed - 1.142.4+2.04-1ubuntu26.2 o grub-efi-arm-bin - 2.04-1ubuntu26.2 o grub-efi-arm64-bin - 2.04-1ubuntu26.2 o grub-efi-arm64-signed - 1.142.4+2.04-1ubuntu26.2 o grub-efi-ia32-bin - 2.04-1ubuntu26.2 Ubuntu 18.04 o grub-efi-amd64-bin - 2.02-2ubuntu8.17 o grub-efi-amd64-signed - 1.93.19+2.02-2ubuntu8.17 o grub-efi-arm-bin - 2.02-2ubuntu8.17 o grub-efi-arm64-bin - 2.02-2ubuntu8.17 o grub-efi-arm64-signed - 1.93.19+2.02-2ubuntu8.17 o grub-efi-ia32-bin - 2.02-2ubuntu8.17 o grub-efi-ia64-bin - 2.02-2ubuntu8.17 Ubuntu 16.04 o grub-efi-amd64-bin - 2.02~beta2-36ubuntu3.27 o grub-efi-amd64-signed - 1.66.27+2.02~beta2-36ubuntu3.27 o grub-efi-arm-bin - 2.02~beta2-36ubuntu3.27 o grub-efi-arm64-bin - 2.02~beta2-36ubuntu3.27 o grub-efi-arm64-signed - 1.66.27+2.02~beta2-36ubuntu3.27 o grub-efi-ia32-bin - 2.02~beta2-36ubuntu3.27 o grub-efi-ia64-bin - 2.02~beta2-36ubuntu3.27 Ubuntu 14.04 o grub-efi-amd64-bin - 2.02~beta2-9ubuntu1.17 o grub-efi-amd64-signed - 1.34.20+2.02~beta2-9ubuntu1.17 o grub-efi-arm-bin - 2.02~beta2-9ubuntu1.17 o grub-efi-arm64-bin - 2.02~beta2-9ubuntu1.17 o grub-efi-ia32-bin - 2.02~beta2-9ubuntu1.17 o grub-efi-ia64-bin - 2.02~beta2-9ubuntu1.17 Fully mitigating these vulnerabilities requires both an updated GRUB2 boot loader and the application of a UEFI Revocation List (dbx) to system firmware. Ubuntu will provide a packaged dbx update at a later time, though system adminstrators may choose to apply a third party dbx update before then. For more details on mitigation steps and the risks entailed (especially for dual/multi-boot scenarios), please see the Knowledge Base article at https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/GRUB2SecureBootBypass References o https://launchpad.net/bugs/1889556 o https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/GRUB2SecureBootBypass - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBXyt/ouNLKJtyKPYoAQihmxAAh4VJ8hTmkypsXlE3I7zyKW1WTP/LTAM5 9AeTw+0k5Q5vUGExHeq9HaDc0tObau8d1Ys12Lq4kt0navKbSi71rVM7hH+5uE5f +9UJcw6LC6fE1zLtrAQMV8xR7X9w+M9Wq8Z97DzvTtNFSammvChfI4YyrCb8Ednk i9jYrER0HeO2HtVgioX6ucFREok+B/POw3PF9yyZmtoCC960+fLKnFGsqUeDO02A snyggzngjMgkeVE4SokkQJKQdmWO42ox7UtNme67jbkBS2zZcLjKo+SGsKjmHnDJ BBLuuXEIO5Z4l6wobxfTOAChK30rBWBx6fbLpzCeWj2RNvbZ6GuFTiQ8vVo9mOeh 6BHpjg5IeQFTXqijOLi9l9u30Es+5aNhlpdVK2jhd/SybdaT9CuMGryVjeMaSt6C AUkBpl1SObcUS0FZ8uGrR0BtFLd2DdotD5ClJcs30hBpYQuRebsWEcMOq3db1Kv7 ebCiPQChtmkYsOvdwMRgn+vP0gQapj26CG58FAU0V/k/VaO3A7SZWqXrR3dKfXdC ZJiqv4R2fK+InJ/hjjDIOec4O6uZ0m1HvZho7lqhfpGcQXa2xQ8zjCW7o49KGwGf OUQEw0hVgJdGanpX7IOMDf2tUsbU43+xfdDX10R7FZ/MaAiR/5i+s4hPySu3gVI/ 1dxuX4Pik0k= =ySLV -----END PGP SIGNATURE-----