CVE-2026-53402 (GCVE-0-2026-53402)
Vulnerability from cvelistv5 – Published: 2026-07-19 12:02 – Updated: 2026-08-17 04:50
VLAI
EPSS
VEX
Title
fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()
Summary
In 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.
Severity
7.1 (High)
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
868749a7456dc48e93887a8474194e2ee6d6c21f , < cb016bcb40c81e7b19c4ae6143babb366dae8e20
(git)
Affected: ebd6f886aa2447fcfcdce5450c9e1028e1d681bb , < ac562193c36696513ae196171892e9338475c4bc (git) Affected: a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 , < 3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5 (git) Affected: a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 , < a7a526fbc847f07ad3a503c7382189be5ab68574 (git) Affected: a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 , < b5bb2c696e140c399cb874def2feedf61dee27d6 (git) Affected: a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 , < 076b1aa65f77a49bce5a48a4a55a397cfcafa2b8 (git) Affected: a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 , < 39815715cbcfabb16fc8c5f4a23deeda20f5df62 (git) Affected: a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 , < 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2 (git) Affected: f08ccb792d3eaf1dc62d8cbf6a30d6522329f660 (git) Affected: 5.10.249 , < 5.10.261 (semver) Affected: 5.15.64 , < 5.15.212 (semver) Affected: 5.19.6 , < 5.20 (semver) |
guessed | |
| Linux | Linux |
Affected:
6.0
Unaffected: 0 , < 6.0 (semver) Unaffected: 5.10.261 , ≤ 5.10.* (semver) Unaffected: 5.15.212 , ≤ 5.15.* (semver) Unaffected: 6.1.178 , ≤ 6.1.* (semver) Unaffected: 6.6.145 , ≤ 6.6.* (semver) Unaffected: 6.12.96 , ≤ 6.12.* (semver) Unaffected: 6.18.39 , ≤ 6.18.* (semver) Unaffected: 7.1.3 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix) |
guessed |
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"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-\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."
}
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"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\u2194512 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-\u003esignal-\u003etty == 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\u0027s 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."
}
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"criteria": "cpe:2.3:o:linux:linux_kernel:6.0:-:*:*:*:*:*:*",
"matchCriteriaId": "7BE551E5-89CF-47A8-9B26-03CE727FBA37",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.0:rc3:*:*:*:*:*:*",
"matchCriteriaId": "A46498B3-78E1-4623-AAE1-94D29A42BE4E",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.0:rc4:*:*:*:*:*:*",
"matchCriteriaId": "F8446E87-F5F6-41CA-8201-BAE0F0CA6DD9",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.0:rc5:*:*:*:*:*:*",
"matchCriteriaId": "8E5FB72F-67CE-43CC-83FE-541604D98182",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.0:rc6:*:*:*:*:*:*",
"matchCriteriaId": "3A0A7397-F5F8-4753-82DC-9A11288E696D",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:6.0:rc7:*:*:*:*:*:*",
"matchCriteriaId": "E6DE049A-ABA8-41DD-988C-8C088358EE9B",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"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-\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": "CVE-2026-53402",
"lastModified": "2026-08-17T05:17:15.080",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.1,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.2,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-07-19T12:16:51.387",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/076b1aa65f77a49bce5a48a4a55a397cfcafa2b8"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/3618a4c5b2591cfa83efe74f5b18c2d02b35c3f5"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/39815715cbcfabb16fc8c5f4a23deeda20f5df62"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/a7a526fbc847f07ad3a503c7382189be5ab68574"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/ac562193c36696513ae196171892e9338475c4bc"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/b5bb2c696e140c399cb874def2feedf61dee27d6"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/cb016bcb40c81e7b19c4ae6143babb366dae8e20"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-125"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-07-20T15:44:48+00:00",
"cve": "CVE-2026-53402",
"id": "CVE-2026-53402",
"initial_release_date": "2026-07-19T00:00:00+00:00",
"product_status:known_affected": "184",
"product_status:known_not_affected": "90",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53402.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "important",
"current_release_date": "2026-09-10T16:55:19Z",
"cve": "CVE-2026-53402",
"id": "CVE-2026-53402",
"initial_release_date": "2026-07-19T17:35:55Z",
"product_status:first_fixed": "2",
"product_status:known_affected": "431",
"product_status:known_not_affected": "147",
"product_status:recommended": "446",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-53402",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-53402.json",
"version": "22"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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