{"id":"CVE-2026-98838","state":"PUBLISHED","title":"vt: skip screen update for DEC alignment test on backgroup consoles","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nvt: skip screen update for DEC alignment test on backgroup consoles\n\n[BUG]\nRecently, we encountered a KASAN warning as follows:\n\nBUG: KASAN: slab-out-of-bounds in fb_pad_aligned_buffer+0x11f/0x140\nRead of size 1 at addr ff1100015fd9f6a4 by task tty_fbcon_oob/1239\nCPU: 7 UID: 0 PID: 1239 Comm: tty_fbcon_oob Not tainted 7.3.0-rc1 #100 PREEMPT(full)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014\nCall Trace:\n <TASK>\n ...\n kasan_report+0xf0/0x120\n fb_pad_aligned_buffer+0x11f/0x140\n ccw_putcs+0x86c/0xa80\n fbcon_putcs+0x338/0x410\n do_update_region+0x21d/0x450\n do_con_write+0x1e0e/0x4880\n con_write+0x13/0x80\n n_tty_write+0x374/0x1010\n file_tty_write.isra.0+0x404/0x7a0\n ...\n\nreproduce:\n1) open /dev/tty0, set a KDFONTOP ioctl with op.op = KD_FONT_OP_SET,\nop.width = 8 and op.height = 16 (visible VC1)\n2) open /dev/tty1, set a KDFONTOP ioctl with op.op = KD_FONT_OP_SET,\nop.width = 28 and op.height = 24 (invisible VC2)\n3) echo 3 > /sys/devices/virtual/graphics/fbcon/rotate_all\n4) write EShash8(esc hash8) to tty1\n\n[CAUSE]\nAll VCs render to the framebuffer. setfont only modifies the target VC's\nfont without resizing the framebuffer backing buffer (par->rotated.buf);\nthe buffer is only resized for the visible VC\n(fbcon_do_set_font -> ... -> vc_do_resize -> update_screen). This relies on\nthe con_should_update() check performed before every update_region().\n\nHowever, the ESC # 8 path (do_con_trol -> do_update_region) omits the\ncon_should_update() check. After changing the font size of an invisible VC,\ndo_update_region() fills using the new font size against a buffer that was\nnever resized, causing an out-of-bounds access.\n\n[FIX]\nOnly push the update when the console is visible and not blanked, add\nthe con_should_update() check in the do_con_trol() like every other call\nsite of do_update_region() (update_region(), invert_screen(), ...).","publishedAt":"2026-10-18T15:50:07.004Z","updatedAt":"2026-10-30T12:40:07.684Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"d388658505bf707ff0cd7142c37c868febf8c2a5","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"82561eee12a342994daf3a70590f5d07c35da743","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"663cf98baced6941a0f3f00e1be61024e57d4429","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"2fc4e71aefab57c80ccc9775aad2af503fc90810","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"985c000b046ca4ee11ee34ef85db500c569ef6e8","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"ad06f7312d3f615dd466483ce81a9b9619166686","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"0ee53081425a1a31ce15089012cd96b8353eb44e","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"0928ed9bd7946baee911efa401088697836e3b1e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/tty/vt/vt.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.12","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.56","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/tty/vt/vt.c"]}],"references":["https://git.kernel.org/stable/c/d388658505bf707ff0cd7142c37c868febf8c2a5","https://git.kernel.org/stable/c/82561eee12a342994daf3a70590f5d07c35da743","https://git.kernel.org/stable/c/663cf98baced6941a0f3f00e1be61024e57d4429","https://git.kernel.org/stable/c/2fc4e71aefab57c80ccc9775aad2af503fc90810","https://git.kernel.org/stable/c/985c000b046ca4ee11ee34ef85db500c569ef6e8","https://git.kernel.org/stable/c/ad06f7312d3f615dd466483ce81a9b9619166686","https://git.kernel.org/stable/c/0ee53081425a1a31ce15089012cd96b8353eb44e","https://git.kernel.org/stable/c/0928ed9bd7946baee911efa401088697836e3b1e"],"weaknesses":[],"ingestedAt":"2026-10-30T13:00:06.648Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98838.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98838","state":"PUBLISHED","datePublished":"2026-10-18T15:50:07.004Z","dateUpdated":"2026-10-30T12:40:07.684Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.373Z"},"containers":{"cna":{"title":"vt: skip screen update for DEC alignment test on backgroup consoles","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nvt: skip screen update for DEC alignment test on backgroup consoles\n\n[BUG]\nRecently, we encountered a KASAN warning as follows:\n\nBUG: KASAN: slab-out-of-bounds in fb_pad_aligned_buffer+0x11f/0x140\nRead of size 1 at addr ff1100015fd9f6a4 by task tty_fbcon_oob/1239\nCPU: 7 UID: 0 PID: 1239 Comm: tty_fbcon_oob Not tainted 7.3.0-rc1 #100 PREEMPT(full)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014\nCall Trace:\n <TASK>\n ...\n kasan_report+0xf0/0x120\n fb_pad_aligned_buffer+0x11f/0x140\n ccw_putcs+0x86c/0xa80\n fbcon_putcs+0x338/0x410\n do_update_region+0x21d/0x450\n do_con_write+0x1e0e/0x4880\n con_write+0x13/0x80\n n_tty_write+0x374/0x1010\n file_tty_write.isra.0+0x404/0x7a0\n ...\n\nreproduce:\n1) open /dev/tty0, set a KDFONTOP ioctl with op.op = KD_FONT_OP_SET,\nop.width = 8 and op.height = 16 (visible VC1)\n2) open /dev/tty1, set a KDFONTOP ioctl with op.op = KD_FONT_OP_SET,\nop.width = 28 and op.height = 24 (invisible VC2)\n3) echo 3 > /sys/devices/virtual/graphics/fbcon/rotate_all\n4) write EShash8(esc hash8) to tty1\n\n[CAUSE]\nAll VCs render to the framebuffer. setfont only modifies the target VC's\nfont without resizing the framebuffer backing buffer (par->rotated.buf);\nthe buffer is only resized for the visible VC\n(fbcon_do_set_font -> ... -> vc_do_resize -> update_screen). This relies on\nthe con_should_update() check performed before every update_region().\n\nHowever, the ESC # 8 path (do_con_trol -> do_update_region) omits the\ncon_should_update() check. After changing the font size of an invisible VC,\ndo_update_region() fills using the new font size against a buffer that was\nnever resized, causing an out-of-bounds access.\n\n[FIX]\nOnly push the update when the console is visible and not blanked, add\nthe con_should_update() check in the do_con_trol() like every other call\nsite of do_update_region() (update_region(), invert_screen(), ...)."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"d388658505bf707ff0cd7142c37c868febf8c2a5","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"82561eee12a342994daf3a70590f5d07c35da743","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"663cf98baced6941a0f3f00e1be61024e57d4429","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"2fc4e71aefab57c80ccc9775aad2af503fc90810","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"985c000b046ca4ee11ee34ef85db500c569ef6e8","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"ad06f7312d3f615dd466483ce81a9b9619166686","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"0ee53081425a1a31ce15089012cd96b8353eb44e","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"0928ed9bd7946baee911efa401088697836e3b1e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/tty/vt/vt.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.12","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.56","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/tty/vt/vt.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/d388658505bf707ff0cd7142c37c868febf8c2a5"},{"url":"https://git.kernel.org/stable/c/82561eee12a342994daf3a70590f5d07c35da743"},{"url":"https://git.kernel.org/stable/c/663cf98baced6941a0f3f00e1be61024e57d4429"},{"url":"https://git.kernel.org/stable/c/2fc4e71aefab57c80ccc9775aad2af503fc90810"},{"url":"https://git.kernel.org/stable/c/985c000b046ca4ee11ee34ef85db500c569ef6e8"},{"url":"https://git.kernel.org/stable/c/ad06f7312d3f615dd466483ce81a9b9619166686"},{"url":"https://git.kernel.org/stable/c/0ee53081425a1a31ce15089012cd96b8353eb44e"},{"url":"https://git.kernel.org/stable/c/0928ed9bd7946baee911efa401088697836e3b1e"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:40:07.684Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.12.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.18.56"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}