{"id":"DEBIAN-CVE-2023-52564","details":"In the Linux kernel, the following vulnerability has been resolved:  Revert \"tty: n_gsm: fix UAF in gsm_cleanup_mux\"  This reverts commit 9b9c8195f3f0d74a826077fc1c01b9ee74907239.  The commit above is reverted as it did not solve the original issue.  gsm_cleanup_mux() tries to free up the virtual ttys by calling gsm_dlci_release() for each available DLCI. There, dlci_put() is called to decrease the reference counter for the DLCI via tty_port_put() which finally calls gsm_dlci_free(). This already clears the pointer which is being checked in gsm_cleanup_mux() before calling gsm_dlci_release(). Therefore, it is not necessary to clear this pointer in gsm_cleanup_mux() as done in the reverted commit. The commit introduces a null pointer dereference:  \u003cTASK\u003e  ? __die+0x1f/0x70  ? page_fault_oops+0x156/0x420  ? search_exception_tables+0x37/0x50  ? fixup_exception+0x21/0x310  ? exc_page_fault+0x69/0x150  ? asm_exc_page_fault+0x26/0x30  ? tty_port_put+0x19/0xa0  gsmtty_cleanup+0x29/0x80 [n_gsm]  release_one_tty+0x37/0xe0  process_one_work+0x1e6/0x3e0  worker_thread+0x4c/0x3d0  ? __pfx_worker_thread+0x10/0x10  kthread+0xe1/0x110  ? __pfx_kthread+0x10/0x10  ret_from_fork+0x2f/0x50  ? __pfx_kthread+0x10/0x10  ret_from_fork_asm+0x1b/0x30  \u003c/TASK\u003e  The actual issue is that nothing guards dlci_put() from being called multiple times while the tty driver was triggered but did not yet finished calling gsm_dlci_free().","modified":"2026-09-15T09:02:48.101305972Z","published":"2024-03-02T22:15:48.933Z","upstream":["CVE-2023-52564"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2023-52564"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.64-1"}]}],"versions":["6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2023-52564.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.5.6-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2023-52564.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.5.6-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2023-52564.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"}]}