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

netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()

In DecodeQ931(), the UserUserIE code path reads a 16-bit length from
the packet, then decrements it by 1 to skip the protocol discriminator
byte before passing it to DecodeH323_UserInformation(). If the encoded
length is 0, the decrement wraps to -1, which is then passed as a
large value to the decoder, leading to an out-of-bounds read.

Add a check to ensure len is positive after the decrement.

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-23455
• https://git.kernel.org/stable/c/495e97af9e7249ee02b72bb1d0848a6efc3700f4
• https://git.kernel.org/stable/c/633e8f87dad32263f6a57dccdb873f042c062111
• https://git.kernel.org/stable/c/9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8
• https://git.kernel.org/stable/c/b652b05d51003ac074b912684f9ec7486231717b
• https://git.kernel.org/stable/c/f173d0f4c0f689173f8cdac79991043a4a89bf66
• https://git.kernel.org/stable/c/f5e4f4e4cdb75ec36802059a94195a31f193da60
• https://git.kernel.org/stable/c/2121f5fbe88daff0f1fc5bc47d359426c74b86b0
• https://git.kernel.org/stable/c/65fa92f79677858b14b9e4b7275f26639afe2710