{"id":"DEBIAN-CVE-2023-53503","details":"In the Linux kernel, the following vulnerability has been resolved:  ext4: allow ext4_get_group_info() to fail  Previously, ext4_get_group_info() would treat an invalid group number as BUG(), since in theory it should never happen.  However, if a malicious attaker (or fuzzer) modifies the superblock via the block device while it is the file system is mounted, it is possible for s_first_data_block to get set to a very large number.  In that case, when calculating the block group of some block number (such as the starting block of a preallocation region), could result in an underflow and very large block group number.  Then the BUG_ON check in ext4_get_group_info() would fire, resutling in a denial of service attack that can be triggered by root or someone with write access to the block device.  For a quality of implementation perspective, it's best that even if the system administrator does something that they shouldn't, that it will not trigger a BUG.  So instead of BUG'ing, ext4_get_group_info() will call ext4_error and return NULL.  We also add fallback code in all of the callers of ext4_get_group_info() that it might NULL.  Also, since ext4_get_group_info() was already borderline to be an inline function, un-inline it.  The results in a next reduction of the compiled text size of ext4 by roughly 2k.","modified":"2026-09-15T09:02:51.504427809Z","published":"2025-10-01T12:15:53.917Z","upstream":["CVE-2023-53503"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2023-53503"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.37-1"}]}],"versions":["6.1.27-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2023-53503.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.3.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2023-53503.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.3.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2023-53503.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}