CVE-2026-12235Out-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.

CVSS

6.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H

Weakness (CWE)

CWE-787

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

Not loaded for this CVE

Assigned by

zephyr

NVD analysis

Awaiting Analysis

Record last updated

Aug 12, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

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