GHSA-JXR7-X2HM-5G42
Vulnerability from github – Published: 2026-07-19 12:30 – Updated: 2026-07-24 15:32In the Linux kernel, the following vulnerability has been resolved:
fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()
When fbcon_do_set_font() fails (e.g., due to a memory allocation failure
inside vc_resize() under heavy memory pressure), it jumps to the err_out
label to roll back the console state. However, the current rollback logic
forgets to restore the hi_font state, leading to a severe state machine
corruption.
Earlier in the function, set_vc_hi_font() might be called to change
vc->vc_hi_font_mask and mutate the screen buffer. If vc_resize()
subsequently fails, the err_out path restores vc_font.charcount
but entirely skips rolling back the vc_hi_font_mask and the screen
buffer.
This mismatch leaves the terminal in a desynchronized state. Because
vc_hi_font_mask remains set, the VT subsystem will still accept
character indices greater than 255 from userspace and write them to the
screen buffer. Subsequent rendering calls (e.g., fbcon_putcs()) will
then use these inflated indices to access the reverted, 256-character
font array, leading to a deterministic out-of-bounds read and potential
kernel memory disclosure.
Fix this by adding the missing rollback logic for the hi_font mask
and screen buffer in the error path.
{
"affected": [],
"aliases": [
"CVE-2026-53402"
],
"database_specific": {
"cwe_ids": [
"CWE-125"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-19T12:16:51Z",
"severity": "HIGH"
},
"details": "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-\u003evc_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.",
"id": "GHSA-jxr7-x2hm-5g42",
"modified": "2026-07-24T15:32:42Z",
"published": "2026-07-19T12:30:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53402"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/076b1aa65f77a49bce5a48a4a55a397cfcafa2b8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/39815715cbcfabb16fc8c5f4a23deeda20f5df62"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a7a526fbc847f07ad3a503c7382189be5ab68574"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ac562193c36696513ae196171892e9338475c4bc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b5bb2c696e140c399cb874def2feedf61dee27d6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cb016bcb40c81e7b19c4ae6143babb366dae8e20"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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