CVE-2026-80578
In the Linux kernel, the following vulnerability has been resolved: fbdev: core: Fix pointer desynchronization in fb_io_read() In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to a faulty user buffer), the loop adjusts the chunk…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.12%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In the Linux kernel, the following vulnerability has been resolved: fbdev: core: Fix pointer desynchronization in fb_io_read() In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to a faulty user buffer), the loop adjusts the chunk size 'c' and updates the remaining 'count'. However, the hardware 'src' pointer has already been eagerly advanced by the original chunk size. If the loop is allowed to continue, the read will resume from an incorrect, over-advanced offset. Since the remaining 'count' was only decremented by the successful bytes, this desynchronization causes the next iterations to execute more hardware reads than originally bounded, eventually leading to out-of-bounds I/O reads. Fix this by breaking out of the loop immediately upon a partial copy_to_user(). A partial copy indicates a faulty user buffer, making subsequent read attempts futile. Breaking out ensures we return the number of successfully read bytes without risking out-of-bounds hardware accesses in subsequent mismatched iterations.
- CVSS 3.1
- 7.3 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
- EPSS
- 0.12% probability · 2th percentile
- CISA KEV
- Not listed
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/42a6d8126c194133eafab2b0fd5c8668ebfcba5b
- https://git.kernel.org/stable/c/42bc07b4e5a3c8a02a433388f562a8f46d093e11
- https://git.kernel.org/stable/c/7110b7b794a2aac2c5cf8eb06ebf2af724c74d50
- https://git.kernel.org/stable/c/7ff87a01ae3a8cd0208f7499386998223a8b5dba
- https://git.kernel.org/stable/c/81cc73be40c6f028f1ee3f438ace46afe666dbae
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.