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CVE-2026-43089: xfrm_user: fix info leak in build_mapping()

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-06 · updated 2026-10-15
• Weakness: CWE-401

Description

In the Linux kernel, the following vulnerability has been resolved: xfrm_user: fix info leak in build_mapping() struct xfrm_usersa_id has a one-byte padding hole after the proto field, which ends up never getting set to zero before copying out to userspace. Fix that up by zeroing out the whole structure before setting individual variables.

Affected products

• Linux kernel: from 2.6.29.1 before 6.6.136; from 6.7 before 6.12.83; from 6.13 before 6.18.24; from 6.19 before 6.19.14; 7.0-rc1, 7.0-rc2, 7.0-rc3, 7.0-rc4, 7.0-rc5, 7.0-rc6 (+1) — fixed in 6.12.83, 6.18.24, 6.19.14, 6.6.136

How to fix

Upgrade to a fixed version: Linux kernel 6.12.83, 6.18.24, 6.19.14, 6.6.136. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/1beb76b2053b68c491b78370794b8ff63c8f8c02
• https://git.kernel.org/stable/c/521385cbd50ca9474396d88462fcdfa6489685d9
• https://git.kernel.org/stable/c/5a1a4b049ddde41466ccac0daeec326254b133f2
• https://git.kernel.org/stable/c/700c9622b23c33b5933e6dcea816492c064e4e10
• https://git.kernel.org/stable/c/72a8de41c3eb4dcf22bf3b674ea38fb2f75d6f32
• https://git.kernel.org/stable/c/c2779ae9a3e5a044e5ccd564681511bbbcc5fc0f
• https://git.kernel.org/stable/c/d3125c541a96fb3c0fc7210112684baf22b6c24d
• https://git.kernel.org/stable/c/f779a6b6cdb6e12baa0663063ac59ab2a8f20c0c
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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