UBUNTU-CVE-2026-79979

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Source
https://ubuntu.com/security/CVE-2026-79979
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-79979
Upstream
Published
2026-10-26T00:00:00Z
Modified
2026-10-27T04:17:56Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

The arm64 MMU backend invalidates a single virtual address from the TLB with invalidate_tlb_page() in arch/arm64/core/mmu.c, which issued TLBI VAE1{IS} with an operand of virt >> 12. That operand encodes the ASID in bits [63:48], so the invalidation only ever matched ASID 0 (the kernel page tables) and global entries. Memory domains, however, are allocated ASIDs starting at 1 in arch_mem_domain_init(), and every domain-private leaf created by private_map() is mapped with MT_NG, i.e. non-global. A domain's cached translation therefore survived the invalidation. All callers of invalidate_tlb_page() are demand-paging paths. When the eviction algorithm reclaims a frame, page_frame_prepare_locked() in kernel/mmu.c calls arch_mem_page_out(), which marks the kernel leaf invalid, propagates the invalid descriptor into every domain via sync_domains(), and then flushes only ASID 0. do_page_fault() immediately reuses the very same page frame for the incoming mapping through arch_mem_page_in(). A user thread that had already touched the evicted page — a k_mem_partition added with arch_mem_domain_partition_add(), or its own stack mapped by map_thread_stack() — retains a valid EL0 read/write translation to that physical frame under its own ASID. Unprivileged code running in a user thread can drive memory pressure to force eviction and then keep accessing the stale address, obtaining read and write access to whatever the kernel subsequently placed in that frame: supervisor data, another memory domain's partition, or another thread's stack. This defeats the isolation that CONFIG_USERSPACE is meant to enforce, allowing information disclosure and memory corruption up to full compromise of the system. The fix switches the implementation to TLBI VAAE1{IS}, which matches every ASID and both global and non-global entries, so no domain-tagged translation survives a page out, dirty-bit update or access-flag clear. Exploitation requires an arm64 build with both CONFIG_USERSPACE and CONFIG_DEMAND_PAGING enabled, an active backing store, and at least one demand-paged page that is also privately mapped into a user memory domain. The same commit additionally stops globalize_table() from stripping EL0 permission and non-global attributes off domain-private leaves during paging synchronization, which previously caused user threads to lose access to their own partitions and stacks.

References

Affected packages

Ubuntu:16.04:LTS
zephyr

Package

Name
zephyr
Purl
pkg:deb/ubuntu/zephyr?arch=source&distro=xenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.1.2-1
3.1.2-1build1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "libzephyr4",
            "binary_version":  "3.1.2-1build1"
        },
        {
            "binary_name":  "libzephyr4-krb5",
            "binary_version":  "3.1.2-1build1"
        },
        {
            "binary_name":  "zephyr-clients",
            "binary_version":  "3.1.2-1build1"
        },
        {
            "binary_name":  "zephyr-server",
            "binary_version":  "3.1.2-1build1"
        },
        {
            "binary_name":  "zephyr-server-krb5",
            "binary_version":  "3.1.2-1build1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"
Ubuntu:18.04:LTS
zephyr

Package

Name
zephyr
Purl
pkg:deb/ubuntu/zephyr?arch=source&distro=bionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.1.2-1build1
3.1.2-1build2

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "libzephyr4",
            "binary_version":  "3.1.2-1build2"
        },
        {
            "binary_name":  "libzephyr4-krb5",
            "binary_version":  "3.1.2-1build2"
        },
        {
            "binary_name":  "zephyr-clients",
            "binary_version":  "3.1.2-1build2"
        },
        {
            "binary_name":  "zephyr-server",
            "binary_version":  "3.1.2-1build2"
        },
        {
            "binary_name":  "zephyr-server-krb5",
            "binary_version":  "3.1.2-1build2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"
Ubuntu:20.04:LTS
zephyr

Package

Name
zephyr
Purl
pkg:deb/ubuntu/zephyr?arch=source&distro=focal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.1.2-1build3

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "libzephyr4",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "libzephyr4-krb5",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "zephyr-clients",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "zephyr-server",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "zephyr-server-krb5",
            "binary_version":  "3.1.2-1build3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"
Ubuntu:22.04:LTS
zephyr

Package

Name
zephyr
Purl
pkg:deb/ubuntu/zephyr?arch=source&distro=jammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.1.2-1build3

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "libzephyr4",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "libzephyr4-krb5",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "zephyr-clients",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "zephyr-server",
            "binary_version":  "3.1.2-1build3"
        },
        {
            "binary_name":  "zephyr-server-krb5",
            "binary_version":  "3.1.2-1build3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"
Ubuntu:24.04:LTS
zephyr

Package

Name
zephyr
Purl
pkg:deb/ubuntu/zephyr?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.1.2-1.1
3.1.2-1.1build1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "libzephyr4",
            "binary_version":  "3.1.2-1.1build1"
        },
        {
            "binary_name":  "libzephyr4-krb5",
            "binary_version":  "3.1.2-1.1build1"
        },
        {
            "binary_name":  "zephyr-clients",
            "binary_version":  "3.1.2-1.1build1"
        },
        {
            "binary_name":  "zephyr-server",
            "binary_version":  "3.1.2-1.1build1"
        },
        {
            "binary_name":  "zephyr-server-krb5",
            "binary_version":  "3.1.2-1.1build1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"
Ubuntu:26.04:LTS
zephyr

Package

Name
zephyr
Purl
pkg:deb/ubuntu/zephyr?arch=source&distro=resolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.1.2-1.1build1
3.1.2-4

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "libzephyr4",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "libzephyr4-krb5",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "zephyr-clients",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "zephyr-server",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "zephyr-server-krb5",
            "binary_version":  "3.1.2-4"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"
Ubuntu:26.10
zephyr

Package

Name
zephyr
Purl
pkg:deb/ubuntu/zephyr?arch=source&distro=stonking

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

3.*
3.1.2-4

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "libzephyr4",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "libzephyr4-krb5",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "zephyr-clients",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "zephyr-server",
            "binary_version":  "3.1.2-4"
        },
        {
            "binary_name":  "zephyr-server-krb5",
            "binary_version":  "3.1.2-4"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-79979.json"