fbdev: bitblit: bound-check glyph index in bit_cursor()
In the Linux kernel, the following vulnerability has been resolved: fbdev: bitblit: bound-check glyph index in bit_cursor() bit_cursor() fetches the glyph under the cursor with c = scr_readw(vc_pos); src = vc_font.data + ((c & charmask) * w * height); where charmask is 0x1ff when vc_hi_font_mask is set. The screen buffer value comes directly from scr_readw() and may be larger than the current font's glyph count. Syzkaller triggers this via vcs_write(). The Call Trace shows vcs_write() in vc_screen.c writing an arbitrary 16-bit value with writev() to /dev/vcsa, which vcs_write_buf() in vc_screen.c stores via vcs_scr_writew() without checking charcount. The stored value is later read in bit_cursor() in bitblit.c. When the font is changed from a font with 512 glyphs to a font with 256 glyphs, the screen buffer can retain characters with the high bit set from the previous mode, which could also produce the same out-of-bounds access. BUG: KASAN: global-out-of-bounds in soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70 Read of size 16 at addr ffff800086c57970 Call Trace: soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70 bit_cursor+0xa90/0x1108 drivers/video/fbdev/core/bitblit.c:365 fbcon_cursor+0x344/0x498 drivers/video/fbdev/core/fbcon.c:1427 hide_cursor+0xdc/0x2d0 drivers/tty/vt/vt.c:883 update_region+0x100/0x18c drivers/tty/vt/vt.c:669 vcs_write+0x8ec/0xaf0 drivers/tty/vt/vc_screen.c:685 bit_putcs_aligned() and bit_putcs_unaligned() already clamp th
CVE-2026-74635
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-74635
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "0998a6cb232674408a03e8561dc15aa266b2f53b",
"lessThan": "250159ace2dc53c1bdad267aa8da51b638748700",
"versionType": "git"
},
{
"status": "affected",
"version": "db5c9a162d2f42bcc842b76b3d935dcc050a0eec",
"lessThan": "46336f476484f36145e5117e72d7b590f47433ee",
"versionType": "git"
},
{
"status": "affected",
"version": "c12003bf91fdff381c55ef54fef3e961a5af2545",
"lessThan": "bf750cfeacf4e47ac72dadc7f05839696efb8576",
"versionType": "git"
},
{
"status": "affected",
"version": "9ba1a7802ca9a2590cef95b253e6526f4364477f",
"lessThan": "94134d70abf9273b70499d97d0adc9185ef21091",
"versionType": "git"
},
{
"status": "affected",
"version": "901f44227072be60812fe8083e83e1533c04eed1",
"lessThan": "c1e7351767dd30fc574395c82121e4c67b882da3",
"versionType": "git"
},
{
"status": "affected",
"version": "18c4ef4e765a798b47980555ed665d78b71aeadf",
"lessThan": "bc9db0d879c655d5dfd8add32fd60f13e65d132c",
"versionType": "git"
},
{
"status": "affected",
"version": "18c4ef4e765a798b47980555ed665d78b71aeadf",
"lessThan": "9ea879862e66e354e616028c31b39aa3eb6d35d8",
"versionType": "git"
},
{
"status": "affected",
"version": "18c4ef4e765a798b47980555ed665d78b71aeadf",
"lessThan": "e033cbf3975a8465f879ebd5989dc35b04423a4d",
"versionType": "git"
},
{
"status": "affected",
"version": "a10cede006f9614b465cf25609a8753efbfd45cc",
"versionType": "git"
},
{
"status": "affected",
"version": "efaf89a75a29b2d179bf4fe63ca62852e93ad620",
"versionType": "git"
},
{
"status": "affected",
"version": "5.10.247",
"lessThan": "5.10.265",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.15.197",
"lessThan": "5.15.216",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.1.159",
"lessThan": "6.1.183",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.6.117",
"lessThan": "6.6.152",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.12.58",
"lessThan": "6.12.104",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.4.302",
"lessThan": "5.5",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.17.8",
"lessThan": "6.18",
"versionType": "semver"
}
],
"programFiles": [
"drivers/video/fbdev/core/bitblit.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.18"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.18",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.265",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.152",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.104",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.45",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.9",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/video/fbdev/core/bitblit.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-74635
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #34254 · Revision 1
- Added to Heist Feed
- Publisher date