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Dismissed
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Permalink CVE-2026-12235
6.3 MEDIUM
  • CVSS version (CVSS): 3.1
  • Attack Vector (AV): Local (L)
  • Attack Complexity (AC): High (H)
  • Privileges Required (PR): Low (L)
  • User Interaction (UI): None (N)
  • Scope (S): Unchanged (U)
  • Confidentiality (C): None (N)
  • Integrity (I): High (H)
  • Availability (A): High (H)
  • Modified Attack Vector (MAV): Local (L)
  • Modified Attack Complexity (MAC): High (H)
  • Modified Privileges Required (MPR): Low (L)
  • Modified User Interaction (MUI): None (N)
  • Modified Confidentiality (MC): None (N)
  • Modified Scope (MS): Unchanged (U)
  • Modified Integrity (MI): High (H)
  • Modified Availability (MA): High (H)
updated 1 month, 1 week ago by @LeSuisse Activity log
  • Created suggestion
  • @LeSuisse dismissed (not in Nixpkgs)
Out-of-bounds write in Xtensa llext PLT relocation from malformed ELF (CWE-787)

The Linkable Loadable Extensions (llext) subsystem mis-handles PLT/RELA relocation entries when linking a relocatable (partially-linked) ELF extension. In llext_link_plt() (subsys/llext/llext_link.c), the relocatable branch (tgt != NULL, the path used for Xtensa relocatable objects) computed the patch address as ext->mem[LLEXT_MEM_TEXT] - text.sh_offset + rela.r_offset + tgt->sh_offset and then performed the relocation write there without validating rela.r_offset. Its sibling shared/dynamic branch already rejected out-of-range offsets via llext_file_offset(). rela.r_offset is read directly from the ELF's RELA table, so a crafted entry with an offset larger than the target section makes the write land arbitrarily far outside the extension's text buffer. The result is an attacker-influenced out-of-bounds write (the location via r_offset, the written value being the resolved symbol address) performed in supervisor context at link time, before any extension code runs. The path is reached from llext_load() whenever an application loads an attacker-influenced ELF extension on Xtensa with writable storage; llext is documented to accept extensions of untrusted origin. Impact is supervisor-context memory corruption (integrity and availability loss, and a sandbox-boundary escape for user-mode extensions). Exploitation is gated by the Xtensa relocatable PLT path and writable storage, and turning the out-of-range write into a useful primitive is non-trivial. The fix adds a bound check rejecting any RELA entry whose r_offset >= tgt->sh_size, mirroring the existing validation in the shared branch.

References

Affected products

zephyr
  • <4.4.2

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