CVE-2026-31786 (GCVE-0-2026-31786)
Vulnerability from cvelistv5 – Published: 2026-04-30 10:31 – Updated: 2026-10-19 19:06
VLAI
EPSS
VEX
Title
Buffer overflow in drivers/xen/sys-hypervisor.c
Summary
In the Linux kernel, the following vulnerability has been resolved:
Buffer overflow in drivers/xen/sys-hypervisor.c
The build id returned by HYPERVISOR_xen_version(XENVER_build_id) is
neither NUL terminated nor a string.
The first causes a buffer overflow as sprintf in buildid_show will
read and copy till it finds a NUL.
00000000 f4 91 51 f4 dd 38 9e 9d 65 47 52 eb 10 71 db 50 |..Q..8..eGR..q.P|
00000010 b9 a8 01 42 6f 2e 32 |...Bo.2|
00000017
So use a memcpy instead of sprintf to have the correct value:
00000000 f4 91 51 f4 dd 00 9e 9d 65 47 52 eb 10 71 db 50 |..Q.....eGR..q.P|
00000010 b9 a8 01 42 |...B|
00000014
(the above have a hack to embed a zero inside and check it's
returned correctly).
This is XSA-485 / CVE-2026-31786
Severity
7.8 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:13 UTC
CWE
- CWE-120 - Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Assigner
References
10 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
84b7625728ea311ea35bdaa0eded53c1c56baeaa , < e3af585e1728c917682b6a3de9a69b41fb9194d4
(git)
Affected: 84b7625728ea311ea35bdaa0eded53c1c56baeaa , < 8288d031a01dbacfde3fc643f7be3d23504de64d (git) Affected: 84b7625728ea311ea35bdaa0eded53c1c56baeaa , < f458ba102da97fafca106327086fc95f3fc764cb (git) Affected: 84b7625728ea311ea35bdaa0eded53c1c56baeaa , < 4b4defd2fce3f966c25adabf46644a85558f1169 (git) Affected: 84b7625728ea311ea35bdaa0eded53c1c56baeaa , < 5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a (git) Affected: 84b7625728ea311ea35bdaa0eded53c1c56baeaa , < d5f59216650c51e5e3fcb7517c825bc8047f60ef (git) Affected: 84b7625728ea311ea35bdaa0eded53c1c56baeaa , < 52cecff98bda2c51eed1c6ce9d21c5d6268fb19d (git) Affected: 84b7625728ea311ea35bdaa0eded53c1c56baeaa , < 27fdbab4221b375de54bf91919798d88520c6e28 (git) |
guessed | |
| Linux | Linux |
Affected:
4.13
Unaffected: 0 , < 4.13 (semver) Unaffected: 5.10.254 , ≤ 5.10.* (semver) Unaffected: 5.15.204 , ≤ 5.15.* (semver) Unaffected: 6.1.170 , ≤ 6.1.* (semver) Unaffected: 6.6.137 , ≤ 6.6.* (semver) Unaffected: 6.12.85 , ≤ 6.12.* (semver) Unaffected: 6.18.26 , ≤ 6.18.* (semver) Unaffected: 7.0.3 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix) |
guessed |
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{
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],
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}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Modified",
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"value": "CWE-787"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
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{
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"value": "CWE-120"
}
],
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
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}
},
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"current_release_date": "2026-09-17T08:40:12+00:00",
"cve": "CVE-2026-31786",
"id": "CVE-2026-31786",
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"product_status:fixed": "762",
"product_status:known_affected": "64",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: Buffer overflow in drivers/xen/sys-hypervisor.c",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31786.json",
"version": "3"
},
"vulnrichment": {
"containers": {
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{
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{
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}
],
"title": "CVE Program Container"
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{
"metrics": [
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{
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"version": "2.0.3"
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"descriptions": [
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"cweId": "CWE-120",
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"lang": "en",
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
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"cna": {
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}
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"value": "AV:L - The vulnerable buildid_show path is reached by a local read of /sys/hypervisor/properties/buildid inside a Linux Xen domain. It is not reachable directly from network packets or adjacent/physical interfaces.\nAC:L - Triggering the bug only requires reading a sysfs file, with no race or special timing. Any uncertainty about heap layout affects exploitation details, so the higher-severity low complexity is appropriate.\nPR:L - The sysfs attribute is read-only mode 0444, so any unprivileged local user in the Xen guest can access it. No capability, authentication, or real-root check gates the read path.\nUI:N - No victim action is required beyond the attacker performing the sysfs read. The vulnerable code runs synchronously in the attacker\u0027s read path.\nS:U - The impact is within the Linux Xen guest kernel security authority. This is not a Xen guest-to-host escape or cross-VM boundary violation.\nC:H - The bug performs an out-of-bounds read past the hypervisor build ID and can return adjacent kernel memory through a user-readable sysfs file. The Xen advisory states kernel secrets may be leaked.\nI:H - If no NUL byte is encountered before the PAGE_SIZE sysfs buffer is exceeded, sprintf can write past the sysfs buffer and corrupt kernel memory. The advisory identifies privilege escalation as possible, so high integrity impact is defensible.\nA:H - The out-of-bounds read/write can corrupt kernel memory and crash the guest kernel. The advisory explicitly lists DoS as a possible impact."
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"state": "PUBLISHED"
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}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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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.