{"id":"CVE-2026-53402","state":"PUBLISHED","title":"fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()\n\nWhen fbcon_do_set_font() fails (e.g., due to a memory allocation failure\ninside vc_resize() under heavy memory pressure), it jumps to the `err_out`\nlabel to roll back the console state. However, the current rollback logic\nforgets to restore the `hi_font` state, leading to a severe state machine\ncorruption.\n\nEarlier in the function, `set_vc_hi_font()` might be called to change\n`vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()`\nsubsequently fails, the `err_out` path restores `vc_font.charcount`\nbut entirely skips rolling back the `vc_hi_font_mask` and the screen\nbuffer.\n\nThis mismatch leaves the terminal in a desynchronized state. Because\n`vc_hi_font_mask` remains set, the VT subsystem will still accept\ncharacter indices greater than 255 from userspace and write them to the\nscreen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will\nthen use these inflated indices to access the reverted, 256-character\nfont array, leading to a deterministic out-of-bounds read and potential\nkernel memory disclosure.\n\nFix this by adding the missing rollback logic for the `hi_font` mask\nand screen buffer in the error path.","publishedAt":"2026-07-19T12:02:01.795Z","updatedAt":"2026-10-19T20:07:47.003Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"868749a7456dc48e93887a8474194e2ee6d6c21f","status":"affected","lessThan":"cb016bcb40c81e7b19c4ae6143babb366dae8e20","versionType":"git"},{"version":"ebd6f886aa2447fcfcdce5450c9e1028e1d681bb","status":"affected","lessThan":"ac562193c36696513ae196171892e9338475c4bc","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"a7a526fbc847f07ad3a503c7382189be5ab68574","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"b5bb2c696e140c399cb874def2feedf61dee27d6","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"076b1aa65f77a49bce5a48a4a55a397cfcafa2b8","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"39815715cbcfabb16fc8c5f4a23deeda20f5df62","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2","versionType":"git"},{"version":"f08ccb792d3eaf1dc62d8cbf6a30d6522329f660","status":"affected","versionType":"git"},{"version":"5.10.249","status":"affected","lessThan":"5.10.261","versionType":"semver"},{"version":"5.15.64","status":"affected","lessThan":"5.15.212","versionType":"semver"},{"version":"5.19.6","status":"affected","lessThan":"5.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbcon.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.0","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.96","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.3","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbcon.c"]}],"references":["https://git.kernel.org/stable/c/cb016bcb40c81e7b19c4ae6143babb366dae8e20","https://git.kernel.org/stable/c/ac562193c36696513ae196171892e9338475c4bc","https://git.kernel.org/stable/c/3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5","https://git.kernel.org/stable/c/a7a526fbc847f07ad3a503c7382189be5ab68574","https://git.kernel.org/stable/c/b5bb2c696e140c399cb874def2feedf61dee27d6","https://git.kernel.org/stable/c/076b1aa65f77a49bce5a48a4a55a397cfcafa2b8","https://git.kernel.org/stable/c/39815715cbcfabb16fc8c5f4a23deeda20f5df62","https://git.kernel.org/stable/c/8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2"],"weaknesses":["CWE-125"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/53xxx/CVE-2026-53402.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53402","state":"PUBLISHED","datePublished":"2026-07-19T12:02:01.795Z","dateUpdated":"2026-10-19T20:07:47.003Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-06-09T07:44:35.403Z"},"containers":{"cna":{"title":"fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()\n\nWhen fbcon_do_set_font() fails (e.g., due to a memory allocation failure\ninside vc_resize() under heavy memory pressure), it jumps to the `err_out`\nlabel to roll back the console state. However, the current rollback logic\nforgets to restore the `hi_font` state, leading to a severe state machine\ncorruption.\n\nEarlier in the function, `set_vc_hi_font()` might be called to change\n`vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()`\nsubsequently fails, the `err_out` path restores `vc_font.charcount`\nbut entirely skips rolling back the `vc_hi_font_mask` and the screen\nbuffer.\n\nThis mismatch leaves the terminal in a desynchronized state. Because\n`vc_hi_font_mask` remains set, the VT subsystem will still accept\ncharacter indices greater than 255 from userspace and write them to the\nscreen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will\nthen use these inflated indices to access the reverted, 256-character\nfont array, leading to a deterministic out-of-bounds read and potential\nkernel memory disclosure.\n\nFix this by adding the missing rollback logic for the `hi_font` mask\nand screen buffer in the error path."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"868749a7456dc48e93887a8474194e2ee6d6c21f","status":"affected","lessThan":"cb016bcb40c81e7b19c4ae6143babb366dae8e20","versionType":"git"},{"version":"ebd6f886aa2447fcfcdce5450c9e1028e1d681bb","status":"affected","lessThan":"ac562193c36696513ae196171892e9338475c4bc","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"a7a526fbc847f07ad3a503c7382189be5ab68574","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"b5bb2c696e140c399cb874def2feedf61dee27d6","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"076b1aa65f77a49bce5a48a4a55a397cfcafa2b8","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"39815715cbcfabb16fc8c5f4a23deeda20f5df62","versionType":"git"},{"version":"a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24","status":"affected","lessThan":"8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2","versionType":"git"},{"version":"f08ccb792d3eaf1dc62d8cbf6a30d6522329f660","status":"affected","versionType":"git"},{"version":"5.10.249","status":"affected","lessThan":"5.10.261","versionType":"semver"},{"version":"5.15.64","status":"affected","lessThan":"5.15.212","versionType":"semver"},{"version":"5.19.6","status":"affected","lessThan":"5.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbcon.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.0","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.96","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.3","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/video/fbdev/core/fbcon.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/cb016bcb40c81e7b19c4ae6143babb366dae8e20"},{"url":"https://git.kernel.org/stable/c/ac562193c36696513ae196171892e9338475c4bc"},{"url":"https://git.kernel.org/stable/c/3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5"},{"url":"https://git.kernel.org/stable/c/a7a526fbc847f07ad3a503c7382189be5ab68574"},{"url":"https://git.kernel.org/stable/c/b5bb2c696e140c399cb874def2feedf61dee27d6"},{"url":"https://git.kernel.org/stable/c/076b1aa65f77a49bce5a48a4a55a397cfcafa2b8"},{"url":"https://git.kernel.org/stable/c/39815715cbcfabb16fc8c5f4a23deeda20f5df62"},{"url":"https://git.kernel.org/stable/c/8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","baseScore":7.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerability is reached only through the KDFONTOP ioctl on a framebuffer-console virtual terminal (/dev/ttyN), which is a local syscall path with no network or physical-access vector.\nAC:L - An attacker who controls a session on an fbcon-backed VT can reliably trigger the bug by issuing a font-change ioctl with different dimensions and a 256↔512 glyph transition, then inducing vc_resize() failure through self-controlled memory pressure; no race or victim-dependent timing is required.\nPR:L - KDFONTOP font-set operations require only that the caller owns the controlling TTY (current->signal->tty == tty), which any unprivileged local user with a console or VT session has; CAP_SYS_TTY_CONFIG is not required on that path.\nUI:N - Exploitation requires only the attacker's own ioctl and memory-pressure actions on their TTY; no action by another user or administrator is needed.\nS:U - Impact is confined to kernel memory disclosure and potential kernel crash within the same kernel security authority; there is no VM escape, sandbox escape, or cross-security-boundary effect.\nC:H - The desynchronized hi_font_mask causes deterministic out-of-bounds reads from the kernel font glyph buffer during fbcon rendering (e.g., bit_cursor and rotated putcs paths), enabling disclosure of adjacent kernel memory.\nI:N - The flaw is an out-of-bounds read with console state desynchronization; it does not provide an arbitrary kernel write, code execution, or other data-modification primitive.\nA:H - Out-of-bounds reads from kernel font data can cause kernel page faults and oopses, consistent with the prior syzkaller-reported fbcon font/resize failure class that produced unhandled page faults."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T04:50:55.659Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.249","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15.64","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.12.96"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.18.39"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"7.1.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19.6"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-53402","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:30:33.058892Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-125","lang":"en","type":"CWE","description":"CWE-125 Out-of-bounds Read"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:07:47.003Z"}}]}}}