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TI-2026-79951 Aliases CVE-2026-79979

Stale Zephyr arm64 TLB entries expose reused physical frames

Priority LOW 35CWE-416Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
High
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-416 and the CVSS impact.

Summary

Zephyr versions from 4.3.0 before 4.5.0 on arm64 invalidate only ASID 0 and global TLB entries when the kernel pages memory out, so cached translations of user memory domains survive. A user thread can keep a stale translation to a page frame that demand paging has reclaimed and reused (CWE-416). An unprivileged user thread can then read and write data the kernel later places in that frame, such as supervisor data or another thread's stack, which breaks memory domain isolation.

Written with Claude Haiku 5.5 from the sources below · 2026-11-02

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00103 0th percentileScored 2026-11-07
Fix Fixed zephyr (zephyrproject): 4.5.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
zephyrprojectzephyr4.3.0 to before 4.5.04.5.0Patch availableCNA
  • zephyr Vendorzephyrproject Affected 4.3.0 to before 4.5.0 Fixed in 4.5.0 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:o:zephyrproject:zephyr:*:*:*:*:*:*:*:*——zephyrproject
  • cpe:2.3:o:zephyrproject:zephyr:*:*:*:*:*:*:*:* Versions — — ·zephyrproject

Remediation

Upgrade Zephyr to version 4.5.0 or later, which fixes this flaw.

Written with Claude Haiku 5.5 from the sources below · 2026-11-02

  • Fix · CNA zephyr (zephyrproject) Fixed in 4.5.0

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    zephyrproject zephyr 4.5.0

    4 records Highest priority Priority MEDIUM 1 MEDIUM, 3 LOW

    Other records, highest priority first

    • TI-2026-79949 WireGuard endpoint hijack via unauthenticated packets in ZephyrPriority MEDIUM 41
    • TI-2026-79953 Zephyr DNS resolver reuses one source port, easing spoofingPriority LOW 28
    • TI-2026-79952 Predictable DHCPv4 transaction ID in Zephyr allows spoofed repliesPriority LOW 24

Timeline

  1. 2026-10-23 Threatist record created from CVE-2026-79979
  2. 2026-10-24 Priority changed: MEDIUM → LOW
  3. 2026-11-02 CISA SSVC decision points changed

References

  • TI-2026-04422 Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key CVSS 3.1CRITICAL 9.8
  • TI-2026-01361 dns: memory‑safety issue in the DNS name parser CVSS 3.1CRITICAL 9.8
  • TI-2026-09174 Unterminated URI buffer causes out-of-bounds read in LwM2M firmware pull (Package URI) CVSS 3.1CRITICAL 9.1
  • TI-2026-09168 Stack buffer overflow in `net_ipaddr_parse()` IPv4 address-with-port parsing in `subsys/net/ip/utils.c` CVSS 3.1CRITICAL 9.8
  • TI-2024-09625 net: lib: http_server: Buffer Under-read CVSS 3.1HIGH 8.6
  • TI-2021-02863 Usb bluetooth device ACL read cb buffer overflow CVSS 3.1CRITICAL 9.6
See all 341 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences