CVE-2025-68256: Linux RTL8723BS IE Parser Hardened Against OOB Reads

A newly assigned security record, CVE-2025-68256, closes a dangerous gap in the Linux kernel’s staging Realtek driver for the RTL8723BS wireless chipset by hardening the driver’s Information Element (IE) parser — rtw_get_ie — against an out‑of‑bounds read that could be triggered by a malformed Wi‑Fi frame.

Background / Overview​

The Realtek RTL8723BS driver (staged in the Linux kernel under drivers/staging/rtl8723bs) supports a wide range of SDIO Wi‑Fi devices found in low‑power PCs, single‑board computers and some Android/x86 ports. The driver contains an IE (Information Element) parser function, rtw_get_ie, which processes variable‑length elements inside 802.11 management frames such as beacons, association requests and probe responses. Historically the parser assumed the length byte advertised by each IE was trustworthy; that assumption is the root cause of this vulnerability. Multiple kernel fixes for rtl8723bs were published in mid‑December 2025 to address a cluster of IE parsing issues; CVE‑2025‑68256 documents the specific out‑of‑bounds read in rtw_get_ie, while related CVEs (for example CVE‑2025‑68254 and CVE‑2025‑68255) address other IE parsing weaknesses in the same driver. These changes were tracked in the Linux kernel CVE records and local tracking artifacts.

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What the vulnerability is — technical summary​

• The vulnerable routine, rtw_get_ie, scans a sequence of Information Elements in a received frame. Each IE is structured as a 1‑byte ID, a 1‑byte length, then “len” bytes of payload.
• The vulnerable parser trusted the length byte without confirming that the advertised IE body fit inside the remainder of the received frame buffer. If a malicious or malformed frame advertises a length larger than the remaining bytes in the frame, the parser can advance beyond the buffer end.
• Consequences range from out‑of‑bounds reads (which can leak memory contents) to infinite loops (if malformed lengths repeatedly point the parser to invalid positions), and other undefined behavior in kernel context. The published fix inserts a boundary check: validate that (offset + 2 + len) does not exceed the buffer limit before accepting the IE or advancing to the next element.

This is a classic parsing boundary‑check bug: the IE header is two bytes (ID + length). The attacker manipulates the length field to force the parser to read beyond available data. The kernel fix clamps or rejects IEs whose length would overrun the available buffer, ensuring safe termination of the loop and preventing OOB reads.

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Scope and affected code paths​

Where this shows up​

• The bug lives in the staging rtl8723bs driver code (drivers/staging/rtl8723bs), which is included in many upstream Linux kernels and backported into distribution kernels and device firmware trees. Staging drivers are drivers maintained in the kernel tree for integration testing and eventual promotion but can still ship in widely used kernels.

Related rtl8723bs issues​

• The rtl8723bs driver received several related fixes addressing IE parsing flaws (several CVEs were assigned in the same time frame). Together they harden parsing of Extended Supported Rates (ESR), Supported Rates, and other IEs to avoid both out‑of‑bounds reads and stack buffer overflows. Administrators should treat this as a multi‑CVEs maintenance cluster rather than a single isolated patch.

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Impact assessment​

Attack vector and prerequisites​

• The attack surface is over the air — an attacker must be within radio range and able to transmit 802.11 management frames (beacons, probes, association requests, etc. to a vulnerable station or access point. Because the flaw is in code that processes received wireless frames, it does not require authenticated association in many scenarios: the attacker can craft malformed management frames to target a victim’s wireless adapter. This places the vulnerability in a local network / proximity threat model, but with network characteristics (wireless).

Potential impacts​

• Denial of Service (DoS): An out‑of‑bounds read or infinite parser loop can crash the kernel or hang the networking stack, disrupting connectivity and potentially requiring a reboot.
• Information disclosure: Uncontrolled reads beyond the frame buffer could expose kernel memory contents to the attacker through side channels or crafted responses, depending on surrounding data flows.
• Escalation / code execution: The specific rtw_get_ie bug is described as an out‑of‑bounds read and (for CVE‑2025‑68256) an infinite loop possibility; it is not documented as a direct arbitrary code‑execution vector. However, related rtl8723bs fixes (for example stack buffer issues) were addressed simultaneously, and combined weaknesses in parsing code can, in other contexts, enable more powerful exploits. Treat combined parsing bugs in a kernel driver as high risk until mitigated.

Severity ratings​

• Several vulnerability trackers list the issue as High severity with CVSS v3 base scores around 7.5 (Network attack vector, no privileges required, no user interaction). Individual vendors and the NVD may initially publish their own scoring; practitioners should rely on vendor/distro advisories for operational guidance.

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What was fixed (the patch-level view)​

• The kernel patch adds an explicit bounds check inside rtw_get_ie: before accepting an IE and advancing the parsing pointer, compute and validate that the next offset plus IE header (2 bytes) plus the advertised IE length does not exceed the frame buffer limit. If the check fails, the parser rejects the malformed IE and either skips it safely or terminates parsing.
• The fix also ensures the parser cannot be forced into an infinite loop by malformed IE headers that would otherwise repeatedly bounce the pointer beyond valid ranges.
• These are defensive, minimal changes that preserve functionality for well‑formed frames while ensuring robust behavior for malformed input. Upstream kernel commit references associated with the CVE are included in published advisories. Note: direct access to the raw kernel commit web pages was referenced by canonical advisories; reviewers encountered access restrictions to some git.kernel.org pages while researching. The NVD/OSV advisories summarize the exact fix logic for operational readers.

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Which kernel versions are patched​

Upstream vulnerability records and the OSV conversion indicate the fix was merged and vendor fixes were backported into several kernel lines. Reported fixed versions include:

• fixed in kernel trees starting at 6.12.62, 6.17.12, and 6.18.1 for the relevant branches; kernels prior to these fixes that include the staging rtl8723bs driver are considered vulnerable until a vendor package is applied or a patch is backported.

Distribution packages will vary — enterprise Linux, embedded kernels, Android kernels and vendor OEM images often lag upstream. Administrators should consult their distribution or device vendor for explicit patch and package versions.

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Practical mitigation and detection guidance​

Immediate mitigations (short term)​

• Identify if the driver/module is present
• Check loaded modules: lsmod | grep -i r8723bs
• Check module name: the module for the staging driver is typically r8723bs (module name r8723bs or r8723bs/rtl8723bs depending on packaging). If the module is loaded, your system processes wireless management frames using this codepath.
• Temporarily unload or disable the module (if you can accept loss of Wi‑Fi):
• sudo modprobe -r r8723bs (or sudo rmmod r8723bs) — this will remove the module until next boot. Use with care: it disables the associated Wi‑Fi interface.
• Disable Wi‑Fi hardware as a temporary protective measure where unloading the module is not feasible — for laptops and appliances, turning off Wi‑Fi or switching into airplane mode removes the over‑the‑air attack surface.
• Isolate affected devices from untrusted networks and public Wi‑Fi until patched. Because an attacker needs radio proximity, physically isolating or disabling wireless reduces risk.

Patching (recommended)​

• Apply your distribution or vendor kernel update as soon as packages containing the patched driver are available. Vendor kernel updates are the safest and easiest route for most environments.
• Backport the upstream patch if you operate custom kernels: fetch the upstream kernel commit(s) associated with the CVE and apply them to your vendor kernel tree, then rebuild the kernel or the staging module and deploy after testing.
• Use backported drivers from trusted backport packages (where available). Some distros offer backported driver packages that can be installed without full kernel updates.

Detection and monitoring​

• Audit dmesg and kernel logs for unusual crashes or messages from the rtl8723bs driver. Kernel panics, OOPS reports, and stack traces tied to drivers/staging/rtl8723bs indicate potential triggered events.
• Monitor network environment for suspicious management frames if you operate managed Wi‑Fi infrastructure; specialized wireless IDS/IPS systems can detect anomalies but require tuning to spot malformed IEs.
• Track vendor and distribution advisories for package names and update timelines.

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How to check if your system is affected — step‑by‑step​

• Check kernel version:
• uname -r — note the running kernel version. Cross‑reference against your distro advisory; upstream fixed versions are a guide but packaged versions differ.
• Check whether rtl8723bs module is present or loaded:
• modinfo r8723bs — returns module metadata if installed.
• lsmod | grep r8723bs — shows if it’s currently loaded.
• If present and you cannot immediately patch, consider unloading:
• sudo modprobe -r r8723bs (test that the removal does not break required networking functionality).
• Follow your distro’s security advisory channel (APT/YUM/Zypper/etc. and install applicable kernel and module updates when published.

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Risks and caveats — what to watch for​

• Staged driver status: Because rtl8723bs is in staging, it receives upstream fixes but may be subject to different release timelines in vendor kernels. Embedded devices, IoT appliances and some Android forks often ship older kernel trees; these devices may require OEM firmware updates rather than distro packages. Plan for manufacturer coordination and extended support windows.
• Combined vulnerabilities: While CVE‑2025‑68256 is an OOB read, other associated CVEs addressed stack buffer overflows and similar parsing errors in the same driver (CVE‑2025‑68254, CVE‑2025‑68255). An attacker could combine different defects to increase the impact; patch all related fixes.
• Exploit availability: As of the initial advisories, there were no public exploits widely published tied specifically to this CVE; however, the vulnerability is trivial to test (malformed frames) for a local attacker and the wireless proximity requirement does not eliminate real‑world risk. Treat the presence of the bug as operationally serious and patch promptly.

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For Linux administrators and OEMs — recommended policy steps​

• Prioritize patching for infrastructure and systems using RTL8723BS hardware. Servers and managed APs typically won’t use the RTL8723BS staging module, but laptops, embedded devices and developer SBCs might.
• Issue managed updates: Test and roll out vendor kernel updates, and publish guidance for customers who run custom kernels or embedded builds.
• Document mitigations in knowledge base articles: include how to temporarily unload the module, network isolation steps, and a timeline for expected vendor patches.
• Audit and inventory: Add a searchable configuration item for devices with Realtek RTL8723BS hardware (or module r8723bs / r8723bs) so you can quickly locate at‑risk assets.

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Why this matters to WindowsForum readers​

While this bug is Linux kernel‑centric, the practical security lessons are broadly applicable:

• Device drivers that parse untrusted data — especially from the network or wireless — are frequent sources of kernel‑level vulnerabilities.
• Staging code can and does make its way into shipping kernels and devices; even drivers described as “experimental” can carry high operational risk on mass‑deployed devices.
• Robust input validation and defensive parsing are essential: trust no length byte until it is validated against the buffer bounds.

Forum members who manage dual‑boot systems, run Linux VMs, develop embedded Linux images, or maintain mixed OS environments should ensure their Linux endpoints are patched or mitigated in accordance with the guidance above. Local wireless proximity attacks pose real operational risk in coffee shops, co‑working spaces and unsecured office wings.

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Verification, references and research notes​

• The National Vulnerability Database (NVD) entry for CVE‑2025‑68256 describes the exact parsing defect and the defensive check added — specifically the validation that (offset + 2 + len) does not exceed the frame buffer limit. This summary is consistent across multiple vulnerability trackers.
• The OSV/converted CVE record and associated vulnerability reconciliation list the same fix summary and provide references to the kernel commits that remedied the issue; OSV also notes fixed kernel trees (6.12.62, 6.17.12, 6.18.1). Administrators should map upstream fixed commits to their distro kernels.
• Commercial scanners and security feeds flagged the issue as high/important and included it in their advisories; CVSS and severity estimations are available from Tenable and other vendors, though exact scoring may differ by source.
• Local forum activity and monitoring snapshots show related CVE entries for rtl8723bs and indicate that multiple patches for the driver were processed in the same maintenance window; this corroborates a bundled remediation effort.

Caveat: some public git.kernel.org commit pages referenced by advisories were intermittently inaccessible during research; the upstream advisories and CVE databases summarize the actual fix logic. Readers who require the raw patch diffs should retrieve them directly via a git fetch from the kernel stable repository or inspect distribution patch backports once vendors publish their advisory pages.

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Bottom line and recommended actions​

• Treat CVE‑2025‑68256 as an actionable kernel‑level vulnerability: if you run hardware that uses the rtl8723bs driver (module r8723bs / r8723bs), plan to update.
• Apply vendor/distribution kernel updates as soon as they are available; if a vendor update is not yet published, consider temporarily unloading the module or disabling Wi‑Fi until you can patch.
• Monitor vendor advisories and security feeds for packaged updates and CVE reconciliations; patching multiple related rtl8723bs CVEs in a single maintenance window is the safest approach.

This set of fixes is an example of how disciplined defensive programming (explicit bounds checking and conservative parsing) eliminates an entire class of kernel vulnerabilities — but it also underscores the need for timely kernel updates and careful inventory of device drivers on production systems.

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Source: MSRC Security Update Guide - Microsoft Security Response Center