CVE-2026-53306 tty: hvc_iucv: fix off-by-one in number of supported devices
An off-by-one error in the Linux kernel's hvc_iucv driver allows out-of-bounds memory access, potentially leading to system instability or crashes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53306?
CVE-2026-53306 is a medium-severity vulnerability in Linux kernel, published on 26 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
tty: hvc_iucv: fix off-by-one in number of supported devices
MAX_HVC_IUCV_LINES == HVC_ALLOC_TTY_ADAPTERS == 8. This is the number of entries in: static struct hvc_iucv_private *hvc_iucv_table[MAX_HVC_IUCV_LINES];
Sometimes hvc_iucv_table[] is limited by: (a) if (num > hvc_iucv_devices) // for error detection or (b) for (i = 0; i < hvc_iucv_devices; i++) // in 2 places (so these 2 don't agree; second one appears to be correct to me.)
hvc_iucv_devices can be 0..8. This is a counter. (c) if (hvc_iucv_devices > MAX_HVC_IUCV_LINES)
If hvc_iucv_devices == 8, (a) allows the code to access hvc_iucv_table[8]. Oops.
Weakness: CWE-193
Which versions are affected by CVE-2026-53306?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53306?
Apply the vendor's patch.
Is CVE-2026-53306 being exploited?
There is no known exploitation of CVE-2026-53306 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53306, DEBIAN-CVE-2026-53306, GHSA-v222-hvcr-rghc, ROOT-OS-DEBIAN-11-CVE-2026-53306, ROOT-OS-DEBIAN-12-CVE-2026-53306, ROOT-OS-UBUNTU-2204-CVE-2026-53306 and 2 more.