{"id":"AZL-109056","summary":"CVE-2026-98840 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nvc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF\n\nThe reload of 'vc' added by commit 8fb9ea65c9d1 (\"vc_screen: reload load\nof struct vc_data pointer in vcs_write() to avoid UAF\") sits after the\n'if (ret)' block, so the copy-failure break path exits the loop without\nreloading vc. If the vc was kfree()'d via vc_port_destruct during the\nunlocked copy_from_user() window, the post-loop\n'if (written && vc) vcs_scr_updated(vc)' is reached with a stale\nnon-NULL vc. The '&& vc' guard from commit a287620312dc (\"vc_screen:\nfix null-ptr-deref in vcs_notifier() during concurrent vcs_write\") only\nhandles the NULL case, not this stale-non-NULL case; vcs_notifier() then\nreads param-\u003evc-\u003evc_num from freed memory:\n\n  BUG: KASAN: slab-use-after-free in vcs_notifier+0x7c/0xd0\n  Read of size 2 at addr ffff888007149190\n  Call Trace:\n   vcs_notifier+0x7c/0xd0\n   atomic_notifier_call_chain+0x70/0xa0\n   vcs_scr_updated+0x77/0xa0\n   vcs_write+0x71b/0x7e0\n  Allocated by task: vc_allocate -\u003e con_install -\u003e tty_open\n  Freed by task: kfree \u003c- vt_ioctl (VT_DISALLOCATE -\u003e vc_port_destruct)\n\nMove the reload to immediately after console_lock(), before 'if (ret)',\nso every break path below passes a fresh vc to the post-loop\nvcs_scr_updated().","modified":"2026-10-19T14:16:31.581065287Z","published":"2026-10-18T16:17:38Z","upstream":["CVE-2026-98840"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98840"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-109056.json"}}],"schema_version":"1.9.0"}