5.5

CVE-2025-40300: x86/vmscape: Add conditional IBPB mitigation

Modified
AliasesUBUNTU-CVE-2025-40300USN-7860-1USN-7860-2
Published 11-09-2025Last modified 15-10-2026

Vulnerability summary

CVE-2025-40300 is a medium (CVSS 5.5) vulnerability in debian debian_linux. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 31.8% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.38%
0%100%
Low · +0.03 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 69 · Related 48
DLA-4327-1DLA-4328-1DSA-6008-1DSA-6009-1MGASA-2025-0309MGASA-2025-0310

Timeline

  1. 11-09-2025
    PublishedVulnerability first disclosed.
  2. 15-10-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: x86/vmscape: Add conditional IBPB mitigation VMSCAPE is a vulnerability that exploits insufficient branch predictor isolation between a guest and a userspace hypervisor (like QEMU). Existing mitigations already protect kernel/KVM from a malicious guest. Userspace can additionally be protected by flushing the branch predictors after a VMexit. Since it is the userspace that consumes the poisoned branch predictors, conditionally issue an IBPB after a VMexit and before returning to userspace. Workloads that frequently switch between hypervisor and userspace will incur the most overhead from the new IBPB. This new IBPB is not integrated with the existing IBPB sites. For instance, a task can use the existing speculation control prctl() to get an IBPB at context switch time. With this implementation, the IBPB is doubled up: one at context switch and another before running userspace. The intent is to integrate and optimize these cases post-embargo. [ dhansen: elaborate on suboptimal IBPB solution ]

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.38%

Chance of exploitation in the next 30 days

Percentile

32%

Versus all other CVEs

30-day change

Increase +0.03 pp

From 0.35% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu149 products
  • linux< 3.13.0-208.259 | < 4.4.0-274.308 | < 4.15.0-243.255 | < 5.4.0-223.243 | < 6.8.0-87.88 | < 5.15.0-161.171
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 4.4.0-1149.155 | < 4.4.0-1187.202 | < 4.15.0-1186.199 | < 5.4.0-1152.162 | < 6.8.0-1042.44 | < 5.15.0-1096.103
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Debian2 products
  • linux< 6.1.153-1 | < 6.12.48-1 | < 6.16.7-1
  • debian_linuxEOL11.0
Linux2 products
  • linux≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < ac60717f9a8d21c58617d0b34274babf24135835 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < c08192b5d6730a914dee6175bc71092ee6a65f14 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < d5490dfa35427a2967e00a4c7a1b95fdbc8ede34 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 15006289e5c38b2a830e1fba221977a27598176c | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 893387c18612bb452336a5881da0d015a7e8f4a2 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < f866eef8d1c65504d30923c3f14082ad294d0e6d | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 34e5667041050711a947e260fc9ebebe08bddee5 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < d7ddc93392e4a7ffcccc86edf6ef3e64c778db52 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 459274c77b37ac63b78c928b4b4e748d1f9d05c8 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 510603f504796c3535f67f55fb0b124a303b44c8 | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 9c23a90648e831d611152ac08dbcd1283d405e7f | ≥ 15d45071523d89b3fb7372e2135fbd72f6af9506, < 2f8f173413f1cbf52660d04df92d0069c4306d25 | c51f1e5f57cca88d8d5894b6fad1638f643a99d0 | 4b3870c343a82cd2df7192cc5149c87205dcc611 | ≥ 3.16.57, < 3.17 | ≥ 4.4.168, < 4.5 | 4.16
  • linux_kernel≥ 3.16.57, < 3.17 | ≥ 4.4.168, < 4.5 | ≥ 4.16, < 5.10.244 | ≥ 5.11, < 5.15.193 | ≥ 5.16, < 6.1.152 | ≥ 6.2, < 6.6.106 | ≥ 6.7, < 6.12.47 | ≥ 6.13, < 6.16.7 | 6.17:rc1 | 6.17:rc2 | 6.17:rc3 | 6.17:rc4 | 6.17:rc5
Opensuse1 product
  • kernel-source&distro=openSUSE Tumbleweed< 6.16.7-1.1

4 vendors · 154 products

References

68 links
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