UBUNTU-CVE-2026-64565: Buffer Overflow
In the Linux kernel, the following vulnerability has been resolved: Input: ims-pcu - fix heap-buffer-overflow in imspcuprocessdata() The imspcuprocessdata() processes incoming URB data byte by byte. However, it fails to check if the readpos index exceeds IMSPCUBUFSIZE. If a malicious USB device sends a packet larger than IMSPCUBUFSIZE, readpos will increment indefinitely. Moreover, since readpos is located immediately after readbuf, the attacker can overwrite readpos itself to arbitrarily control the index. This manipulated readpos is subsequently used in imspcuhandleresponse() to copy data into cmdbuf, leading to a heap buffer overflow. Specifically, an attacker can overwrite the cmddone.wait.head located at offset 136 relative to cmdbuf in the imspcuhandleresponse(). Consequently, when the driver calls complete(&pcu->cmddone), it triggers a control flow hijack by using the manipulated pointer. Fix this by adding a bounds check for readpos before writing to readbuf. If the packet is too long, discard it, log a warning, and reset the parser state. [dtor: factor out resetting packet state, reset checksum as well]
Affected Software
Remediation
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
In ims_pcu_process_data(), check that read_pos is less than IMS_PCU_BUF_SIZE before writing to read_buf. If the packet exceeds IMS_PCU_BUF_SIZE, discard it, log a warning, reset the parser state, and reset the checksum.
Event History
Frequently Asked Questions
What access does an attacker need to exploit this issue?
The attacker needs to present a malicious USB device that can send an oversized packet to the IMS PCU input driver. The issue is triggered by incoming URB data exceeding IMS_PCU_BUF_SIZE.
What is the potential impact of successful exploitation?
An oversized USB packet can cause a heap buffer overflow and allow manipulation of the command-completion wait queue pointer. When the driver completes the command, this can result in control-flow hijacking.
Which Ubuntu kernel package families are listed as affected?
The listed package families are ubuntu/linux, ubuntu/linux-fips, ubuntu/linux-aws, ubuntu/linux-azure, ubuntu/linux-aws-fips, ubuntu/linux-azure-fips, ubuntu/linux-gcp, and ubuntu/linux-gcp-fips.
What does the fix do when it receives an oversized packet?
The fix checks read_pos before writing to read_buf. Packets that are too long are discarded, a warning is logged, and the parser state and checksum are reset.