{"id":"CVE-2026-98840","title":"vc_screen: reload vc pointer before if (ret) in vcs_write() to avoid UAF","summary":"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 poi…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 73049768ad57145acd337102c5aa3c788e6642c8 < 1485a3dd97ab1af2605243cabe6b604546d46dd1","Linux >= 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde < 233a2e190b12884d186027d0b86d43a48799b69c","Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a < 9dfcadc5e003fb250dd471db90144bd5366140e9","Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a < 226bd5603371cd9f6642cbb9e9a677f445de3530","Linux 43a6281790273c1b0a9ab76609ff0245b968f1e6","Linux b6bbb85cf45bf0b070e741997fe0af3a772c5ad5","Linux ff4806202749a51938236214adc0281481a57366","Linux 8232fca738011ca2ec865b46ec721d1796dc0580","Linux 74be188eb2dc1c99d63986167b9a67d415fe7326","Linux 09a43e81279b8da15526da09877134b8bcf618b0","Linux >= 6.12.95 < 6.12.113","Linux >= 6.18.37 < 6.18.56","Linux >= 5.10.260 < 5.11","Linux >= 5.15.211 < 5.16","Linux >= 6.1.177 < 6.2","Linux >= 6.6.144 < 6.7","Linux >= 7.0.14 < 7.1","Linux >= 7.1.2 < 7.2","Linux 7.2"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:50:14.029Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98840","references":[{"url":"https://git.kernel.org/stable/c/1485a3dd97ab1af2605243cabe6b604546d46dd1"},{"url":"https://git.kernel.org/stable/c/233a2e190b12884d186027d0b86d43a48799b69c"},{"url":"https://git.kernel.org/stable/c/9dfcadc5e003fb250dd471db90144bd5366140e9"},{"url":"https://git.kernel.org/stable/c/226bd5603371cd9f6642cbb9e9a677f445de3530"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T16:47:32.468Z","slug":"CVE-2026-98840","body":"## Overview\n\nIn 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->vc->vc_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 -> con_install -> tty_open\n  Freed by task: kfree <- vt_ioctl (VT_DISALLOCATE -> 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().\n\n## Affected\n\n- `Linux >= 73049768ad57145acd337102c5aa3c788e6642c8 < 1485a3dd97ab1af2605243cabe6b604546d46dd1`\n- `Linux >= 7cc3dd79777f6ae4625ec37e84dd18a26dc88bde < 233a2e190b12884d186027d0b86d43a48799b69c`\n- `Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a < 9dfcadc5e003fb250dd471db90144bd5366140e9`\n- `Linux >= a287620312dc6dcb9a093417a0e589bf30fcf38a < 226bd5603371cd9f6642cbb9e9a677f445de3530`\n- `Linux 43a6281790273c1b0a9ab76609ff0245b968f1e6`\n- `Linux b6bbb85cf45bf0b070e741997fe0af3a772c5ad5`\n- `Linux ff4806202749a51938236214adc0281481a57366`\n- `Linux 8232fca738011ca2ec865b46ec721d1796dc0580`\n- `Linux 74be188eb2dc1c99d63986167b9a67d415fe7326`\n- `Linux 09a43e81279b8da15526da09877134b8bcf618b0`\n- `Linux >= 6.12.95 < 6.12.113`\n- `Linux >= 6.18.37 < 6.18.56`\n- `Linux >= 5.10.260 < 5.11`\n- `Linux >= 5.15.211 < 5.16`\n- `Linux >= 6.1.177 < 6.2`\n- `Linux >= 6.6.144 < 6.7`\n- `Linux >= 7.0.14 < 7.1`\n- `Linux >= 7.1.2 < 7.2`\n- `Linux 7.2`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}