CVE-2026-43197

In the Linux kernel, the following vulnerability has been resolved:

netconsole: avoid OOB reads, msg is not nul-terminated

msg passed to netconsole from the console subsystem is not guaranteed to be nul-terminated. Before recent commit 7eab73b18630 (netconsole: convert to NBCON console infrastructure) the message would be placed in printk_shared_pbufs, a static global buffer, so KASAN had harder time catching OOB accesses. Now we see:

printk: console [netcon_ext0] enabled
BUG: KASAN: slab-out-of-bounds in string+0x1f7/0x240
Read of size 1 at addr ffff88813b6d4c00 by task pr/netcon_ext0/594

CPU: 65 UID: 0 PID: 594 Comm: pr/netcon_ext0 Not tainted 6.19.0-11754-g4246fd6547c9
Call Trace:
 kasan_report+0xe4/0x120
 string+0x1f7/0x240
 vsnprintf+0x655/0xba0
 scnprintf+0xba/0x120
 netconsole_write+0x3fe/0xa10
 nbcon_emit_next_record+0x46e/0x860
 nbcon_kthread_func+0x623/0x750

Allocated by task 1:
 nbcon_alloc+0x1ea/0x450
 register_console+0x26b/0xe10
 init_netconsole+0xbb0/0xda0

The buggy address belongs to the object at ffff88813b6d4000
            which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 0 bytes to the right of
            allocated 3072-byte region [ffff88813b6d4000, ffff88813b6d4c00)

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/3126a2f98beaec5a554a1fb31c46db1e8542665e
• https://git.kernel.org/stable/c/74ab1456eaa3b2eb986138f9e1f4cb37e73b6f58
• https://git.kernel.org/stable/c/82aec772fca2223bc5774bd9af486fd95766e578