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CVE-2026-31786— Buffer overflow in drivers/xen/sys-hypervisor.c

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于xen系统超管理器驱动中缓冲区溢出，可能导致信息泄露。

CVSS 7.8 · High EPSS 0.21% · P10

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 84b7625728ea311ea35bdaa0eded53c1c56baeaa< e3af585e1728c917682b6a3de9a69b41fb9194d4 affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa< 8288d031a01dbacfde3fc643f7be3d23504de64d affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa< f458ba102da97fafca106327086fc95f3fc764cb affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa< 4b4defd2fce3f966c25adabf46644a85558f1169 affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa< 5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa< d5f59216650c51e5e3fcb7517c825bc8047f60ef affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa< 52cecff98bda2c51eed1c6ce9d21c5d6268fb19d affected
84b7625728ea311ea35bdaa0eded53c1c56baeaa< 27fdbab4221b375de54bf91919798d88520c6e28 affected
… +10 more rows
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I. Basic Information for CVE-2026-31786

Vulnerability Information
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Vulnerability Title
Buffer overflow in drivers/xen/sys-hypervisor.c
Source: CVE Program / CVE List V5
Vulnerability Description
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
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于xen系统超管理器驱动中缓冲区溢出，可能导致信息泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 84b7625728ea311ea35bdaa0eded53c1c56baeaa ~ e3af585e1728c917682b6a3de9a69b41fb9194d4 -
Linux Linux 4.13 -

II. Public POCs for CVE-2026-31786

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III. Intelligence Information for CVE-2026-31786

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Patches & Fixes for CVE-2026-31786 (8)

Same Patch Batch · Linux · 2026-04-30 · 4 CVEs total

CVE-2026-31693 7.8 HIGH cifs: some missing initializations on replay
CVE-2026-31692 rtnetlink: add missing netlink_ns_capable() check for peer netns
CVE-2026-31787 xen/privcmd: fix double free via VMA splitting

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31786

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