CVE-2026-43453

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

netfilter: nft_set_pipapo: fix stack out-of-bounds read in pipapo_drop()

pipapo_drop() passes rulemap[i + 1].n to pipapo_unmap() as the to_offset argument on every iteration, including the last one where i == m->field_count - 1. This reads one element past the end of the stack-allocated rulemap array (declared as rulemap[NFT_PIPAPO_MAX_FIELDS] with NFT_PIPAPO_MAX_FIELDS == 16).

Although pipapo_unmap() returns early when is_last is true without using the to_offset value, the argument is evaluated at the call site before the function body executes, making this a genuine out-of-bounds stack read confirmed by KASAN:

BUG: KASAN: stack-out-of-bounds in pipapo_drop+0x50c/0x57c [nf_tables] Read of size 4 at addr ffff8000810e71a4

This frame has 1 object: [32, 160) rulemap

The buggy address is at offset 164 – exactly 4 bytes past the end of the rulemap array.

Pass 0 instead of rulemap[i + 1].n on the last iteration to avoid the out-of-bounds read.

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/0a55d62cdb628923d8a21724374a70c76ac7d19d
• https://git.kernel.org/stable/c/1957e793196e7f8557374fd4eda53abcbb42e1c0
• https://git.kernel.org/stable/c/324b749aa5b2d516ccfab933df9d3f56e7807f5f
• https://git.kernel.org/stable/c/57fb87ca095d5127cd7a27583b8ec43dcf7c9e9e
• https://git.kernel.org/stable/c/60c1d18781e37bfb96290b86510eb01c5fa24d75
• https://git.kernel.org/stable/c/d6d8cd2db236a9dd13dbc2d05843b3445cc964b5
• https://git.kernel.org/stable/c/dfbdac719198778b581bc0dd055df2542edb8c62
• https://git.kernel.org/stable/c/e047f6fbb975f685d6c9fcef95b3b7787a79b46d