CVE-2026-98540 fprobe: Terminate the fgraph_data list when the reservation is not filled
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-98540?
CVE-2026-98540 is a vulnerability in Linux, published on 18 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
fprobe: Terminate the fgraph_data list when the reservation is not filled
fprobe_fgraph_entry() reserves shadow stack space for every fprobe with an exit handler, but only fills it for those whose entry handler returns 0. fgraph_reserve_data() does not clear the area, so fprobe_return() parses the unused tail as headers left over from an earlier call, and an exit handler can run twice or despite its entry handler asking to skip it.
Write a zero word after the last entry to terminate the walk. A zeroed slot does not decode to a NULL fprobe on the arches that encode the header into one unsigned long, since arch_decode_fprobe_header_fp() ORs in FPROBE_HEADER_MSB_PATTERN, so make read_fprobe_header() return NULL for a zeroed slot.
Which versions are affected by CVE-2026-98540?
How do I fix CVE-2026-98540?
Upgrade to a fixed version.
Is CVE-2026-98540 being exploited?
There is no known exploitation of CVE-2026-98540 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-98540, GHSA-9jj3-9f6g-g6xw, UBUNTU-CVE-2026-98540.