{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-74635", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-74635", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-08-22T15:32:15.280Z", "updatedAt": "2026-10-16T19:06:04.057Z", "importedAt": "2026-10-24T01:58:30.346Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "fbdev: bitblit: bound-check glyph index in bit_cursor()", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: bitblit: bound-check glyph index in bit_cursor()\n\nbit_cursor() fetches the glyph under the cursor with\n\n\tc = scr_readw(vc_pos);\n\tsrc = vc_font.data + ((c & charmask) * w * height);\n\nwhere charmask is 0x1ff when vc_hi_font_mask is set. The screen buffer\nvalue comes directly from scr_readw() and may be larger than the current\nfont's glyph count.\n\nSyzkaller triggers this via vcs_write(). The Call Trace shows\nvcs_write() in vc_screen.c writing an arbitrary 16-bit value with\nwritev() to /dev/vcsa, which vcs_write_buf() in vc_screen.c stores via\nvcs_scr_writew() without checking charcount. The stored value is later\nread in bit_cursor() in bitblit.c.\n\nWhen the font is changed from a font with 512 glyphs to a font with\n256 glyphs, the screen buffer can retain characters with the high\nbit set from the previous mode, which could also produce the same\nout-of-bounds access.\n\n BUG: KASAN: global-out-of-bounds in soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70\n Read of size 16 at addr ffff800086c57970\n\n Call Trace:\n soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70\n bit_cursor+0xa90/0x1108 drivers/video/fbdev/core/bitblit.c:365\n fbcon_cursor+0x344/0x498 drivers/video/fbdev/core/fbcon.c:1427\n hide_cursor+0xdc/0x2d0 drivers/tty/vt/vt.c:883\n update_region+0x100/0x18c drivers/tty/vt/vt.c:669\n vcs_write+0x8ec/0xaf0 drivers/tty/vt/vc_screen.c:685\n\nbit_putcs_aligned() and bit_putcs_unaligned() already clamp the glyph\nindex to vc_font.charcount. Apply the same clamp in bit_cursor() after\nextracting the attribute and masking, before indexing fontdata.\n\nThe fix completes the bounds checking started in commit 18c4ef4e765a\n(\"fbdev: bitblit: bound-check glyph index in bit_putcs*\"), which missed\nthe cursor path.\n\nThis change should be safe because the clamp reuses the existing\ncontract from fbcon: charcount is maintained under console_lock in\ncon_font_set() and fbcon_font_set(), and hi_font_mask is cleared when\nswitching from 512 to 256 glyphs. When stale screen data with high bits\nremains after a font switch, or when vcs_write() stores an arbitrary\nvalue, clamping the index to 0 prevents the out-of-bounds read without\nchanging cursor semantics — the same fallback bit_putcs uses.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "0998a6cb232674408a03e8561dc15aa266b2f53b", "status": "affected", "versionType": "git", "lessThan": "250159ace2dc53c1bdad267aa8da51b638748700" }, { "version": "db5c9a162d2f42bcc842b76b3d935dcc050a0eec", "status": "affected", "versionType": "git", "lessThan": "46336f476484f36145e5117e72d7b590f47433ee" }, { "version": "c12003bf91fdff381c55ef54fef3e961a5af2545", "status": "affected", "versionType": "git", "lessThan": "bf750cfeacf4e47ac72dadc7f05839696efb8576" }, { "version": "9ba1a7802ca9a2590cef95b253e6526f4364477f", "status": "affected", "versionType": "git", "lessThan": "94134d70abf9273b70499d97d0adc9185ef21091" }, { "version": "901f44227072be60812fe8083e83e1533c04eed1", "status": "affected", "versionType": "git", "lessThan": "c1e7351767dd30fc574395c82121e4c67b882da3" }, { "version": "18c4ef4e765a798b47980555ed665d78b71aeadf", "status": "affected", "versionType": "git", "lessThan": "bc9db0d879c655d5dfd8add32fd60f13e65d132c" }, { "version": "18c4ef4e765a798b47980555ed665d78b71aeadf", "status": "affected", "versionType": "git", "lessThan": "9ea879862e66e354e616028c31b39aa3eb6d35d8" }, { "version": "18c4ef4e765a798b47980555ed665d78b71aeadf", "status": "affected", "versionType": "git", "lessThan": "e033cbf3975a8465f879ebd5989dc35b04423a4d" }, { "version": "a10cede006f9614b465cf25609a8753efbfd45cc", "status": "affected", "versionType": "git" }, { "version": "efaf89a75a29b2d179bf4fe63ca62852e93ad620", "status": "affected", "versionType": "git" }, { "version": "5.10.247", "status": "affected", "versionType": "semver", "lessThan": "5.10.265" }, { "version": "5.15.197", "status": "affected", "versionType": "semver", "lessThan": "5.15.216" }, { "version": "6.1.159", "status": "affected", "versionType": "semver", "lessThan": "6.1.183" }, { "version": "6.6.117", "status": "affected", "versionType": "semver", "lessThan": "6.6.152" }, { "version": "6.12.58", "status": "affected", "versionType": "semver", "lessThan": "6.12.104" }, { "version": "5.4.302", "status": "affected", "versionType": "semver", "lessThan": "5.5" }, { "version": "6.17.8", "status": "affected", "versionType": "semver", "lessThan": "6.18" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "6.18", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "6.18" }, { "version": "5.10.265", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.216", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.183", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.152", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.104", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.45", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.1.9", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.1.*" }, { "version": "7.2", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }