Bug 2502338 (CVE-2026-63932)

Summary: CVE-2026-63932 kernel: iio: chemical: mhz19b: reject oversized serial replies
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `mhz19b` driver, which handles Winsen MHZ19B CO2 sensors. The `mhz19b_receive_buf()` function does not properly validate the size of incoming serial replies before copying them into a fixed-size buffer. A remote attacker could exploit this by sending an oversized serial reply, leading to a buffer overflow. This could result in a denial of service or potentially more severe impacts by overwriting critical data within the kernel.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-07-19 16:02:42 UTC 
In the Linux kernel, the following vulnerability has been resolved:

iio: chemical: mhz19b: reject oversized serial replies

mhz19b_receive_buf() appends each serdev chunk into the fixed
MHZ19B_CMD_SIZE receive buffer and advances buf_idx by len without
checking that the chunk fits in the remaining space. A large callback
can therefore overflow st->buf before the command path validates the
reply.

Reset the reply state before each command and reject oversized serial
replies before copying them into the fixed buffer. When an oversized
reply is detected, wake the waiter and report -EMSGSIZE instead of
overwriting st->buf.
Comment 1 Keith Grant 2026-07-21 21:42:01 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071950-CVE-2026-63932-a1df@gregkh/T