CVE-2026-31786: Buffer overflow in drivers/xen/sys-hypervisor.c
Noroxi assessment
Priority: Monitor (action score 31/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: Linux Linux 27fdbab4221b375de54bf91919798d88520c6e28, 4b4defd2fce3f966c25adabf46644a85558f1169, 52cecff98bda2c51eed1c6ce9d21c5d6268fb19d.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to Linux Linux 27fdbab4221b375de54bf91919798d88520c6e28, 4b4defd2fce3f966c25adabf46644a85558f1169, 52cecff98bda2c51eed1c6ce9d21c5d6268fb19d or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
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
- Published
- Apr 30, 2026
- Updated
- Oct 19, 2026
- EPSS
- 0.1% · 9th percentile
- CWE
- CWE-787
Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · Linux
- 7.8
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- linux linux kernel4.13 and later · before 5.10.254
- linux linux kernel5.11 and later · before 5.15.204
- linux linux kernel5.16 and later · before 6.1.170
- linux linux kernel6.2 and later · before 6.6.137
- linux linux kernel6.7 and later · before 6.12.85
- linux linux kernel6.13 and later · before 6.18.26
- linux linux kernel6.19 and later · before 7.0.3
- linux linux kernel7.1
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- 4.13affected
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before e3af585e1728c917682b6a3de9a69b41fb9194d4affected · git
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before 8288d031a01dbacfde3fc643f7be3d23504de64daffected · git
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before f458ba102da97fafca106327086fc95f3fc764cbaffected · git
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before 4b4defd2fce3f966c25adabf46644a85558f1169affected · git
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before 5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0aaffected · git
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before d5f59216650c51e5e3fcb7517c825bc8047f60efaffected · git
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before 52cecff98bda2c51eed1c6ce9d21c5d6268fb19daffected · git
- 84b7625728ea311ea35bdaa0eded53c1c56baeaa and later · before 27fdbab4221b375de54bf91919798d88520c6e28affected · git
- before 4.13not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:10 | kernel | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-core | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-core | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-devel | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-devel-matched | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules-core | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules-extra | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-devel | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-devel-matched | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules-core | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules-extra | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-abi-stablelists | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-core | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-cross-headers | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-debug | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-debug-core | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-debug-devel | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-debug-devel-matched | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-debug-modules | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
| AlmaLinux:10 | kernel-debug-modules-core | before 6.12.0-211.26.1.el10_2 | 6.12.0-211.26.1.el10_2 |
+96
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV90Now
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
Published before and after this one in the same product
- ← EarlierCVE-2026-31691Apr 27, 2026 · igb: remove napi_synchronize() in igb_down()22Monitor
- ← EarlierCVE-2026-31692Apr 30, 2026 · rtnetlink: add missing netlink_ns_capable() check for peer netns22Monitor
- Later →CVE-2026-31787Apr 30, 2026 · xen/privcmd: fix double free via VMA splitting31Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 27fdbab4221b375de54bf91919798d88520c6e28 | Vendor (CNA) |
| Linux Linux | 4b4defd2fce3f966c25adabf46644a85558f1169 | Vendor (CNA) |
| Linux Linux | 52cecff98bda2c51eed1c6ce9d21c5d6268fb19d | Vendor (CNA) |
| Linux Linux | 5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a | Vendor (CNA) |
| Linux Linux | 8288d031a01dbacfde3fc643f7be3d23504de64d | Vendor (CNA) |
| Linux Linux | d5f59216650c51e5e3fcb7517c825bc8047f60ef | Vendor (CNA) |
| Linux Linux | e3af585e1728c917682b6a3de9a69b41fb9194d4 | Vendor (CNA) |
| Linux Linux | f458ba102da97fafca106327086fc95f3fc764cb | Vendor (CNA) |
| almalinux:kernel | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-core | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-core | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-devel | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-devel-matched | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules-core | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-debug-modules-extra | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-devel | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:kernel-64k-devel-matched | 5.14.0-687.13.1.el9_8 · AlmaLinux:9 | Package registry (OSV) |
| alpine:xen | 0 · Alpine:v3.20 | Package registry (OSV) |
| debian:linux | 6.1.170-1 · Debian:12 | Package registry (OSV) |
| red hat:kernel-64k-debug-debuginfo | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-devel | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-debug-devel-matched | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-debuginfo | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-devel | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-64k-devel-matched | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-debug-debuginfo | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:kernel-debug-devel | 0:5.14.0-687.13.1.el9_8 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
+5
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-26-0167 · May 5, 2026(Linux Kernel Güvenlik Bildirimi)
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-787 · Out-of-bounds WriteCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- SSVC exploitation— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (9 more)Show less
- git.kernel.org/stable/c/4b4defd2fce3f966c25adabf46644a85558f1169
- git.kernel.org/stable/c/52cecff98bda2c51eed1c6ce9d21c5d6268fb19d
- git.kernel.org/stable/c/5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a
- git.kernel.org/stable/c/8288d031a01dbacfde3fc643f7be3d23504de64d
- git.kernel.org/stable/c/d5f59216650c51e5e3fcb7517c825bc8047f60ef
- git.kernel.org/stable/c/e3af585e1728c917682b6a3de9a69b41fb9194d4
- git.kernel.org/stable/c/f458ba102da97fafca106327086fc95f3fc764cb
- www.openwall.com/lists/oss-security/2026/04/28/12
- xenbits.xen.org/xsa/advisory-485.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.