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CVE-2026-12235— Out-of-bounds write in Xtensa llext PLT relocation from malformed ELF (CWE-787)

Quick assessment

Affected
zephyrproject zephyr
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

zephyrproject zephyr是zephyrproject组织开源的一个面向物联网设备的实时操作系统。 zephyrproject zephyr 3.7.0版本至4.4.2之前版本存在缓冲区错误漏洞，该漏洞源于llext子系统错误处理PLT/RELA重定位条目，未验证rela.r_offset，可能导致越界写入，进而造成内存破坏（完整性及可用性损失，并可能导致沙箱逃逸）。

CVSS 6.3 · Medium EPSS 0.13% · P2

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 1

VendorProduct Version RangeStatus
zephyrproject zephyr 3.7.0< 4.4.2 affected
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I. Basic Information for CVE-2026-12235

Vulnerability Information
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Vulnerability Title
Out-of-bounds write in Xtensa llext PLT relocation from malformed ELF (CWE-787)
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
zephyrproject zephyr 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
zephyrproject zephyr是zephyrproject组织开源的一个面向物联网设备的实时操作系统。 zephyrproject zephyr 3.7.0版本至4.4.2之前版本存在缓冲区错误漏洞，该漏洞源于llext子系统错误处理PLT/RELA重定位条目，未验证rela.r_offset，可能导致越界写入，进而造成内存破坏（完整性及可用性损失，并可能导致沙箱逃逸）。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
zephyrproject zephyr 3.7.0 ~ 4.4.2 -

II. Public POCs for CVE-2026-12235

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III. Intelligence Information for CVE-2026-12235

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Patches & Fixes for CVE-2026-12235 (1)

Vendor Advisories for CVE-2026-12235 (1)

Same Patch Batch · zephyrproject · 2026-08-12 · 4 CVEs total

CVE-2026-12234 7.8 HIGH TOCTOU double-fetch in `zsock_sendmsg`/`recvmsg` userspace verifiers allows kernel-heap ou
CVE-2026-12232 6.1 MEDIUM Out-of-bounds read via unvalidated stream_id in Intel ALH DAI get_properties
CVE-2026-12233 5.9 MEDIUM Uninitialized mutex in TLS trusted-credential backend causes kernel NULL-deref DoS under c

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-787

V. Comments for CVE-2026-12235

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