CVE-2025-38528: bpf: Reject %p% format string in bprintf-like helpers

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-08-16 · updated 2026-10-15

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Reject %p% format string in bprintf-like helpers static const char fmt[] = "%p%"; bpf_trace_printk(fmt, sizeof(fmt)); The above BPF program isn't rejected and causes a kernel warning at runtime: Please remove unsupported %\x00 in format string WARNING: CPU: 1 PID: 7244 at lib/vsprintf.c:2680 format_decode+0x49c/0x5d0 This happens because bpf_bprintf_prepare skips over the second %, detected as punctuation, while processing %p. This patch fixes it by not skipping over punctuation. %\x00 is then processed in the next iteration and rejected.

Affected products

Debian Linux: 11.0
Linux kernel: from 5.13 before 5.15.190; from 5.16 before 6.1.147; from 6.2 before 6.6.100; from 6.7 before 6.12.40; from 6.13 before 6.15.8; 6.16-rc1, 6.16-rc2, 6.16-rc3, 6.16-rc4, 6.16-rc5, 6.16-rc6 — fixed in 5.15.190, 6.1.147, 6.12.40, 6.15.8, 6.6.100

How to fix

Upgrade to a fixed version: Linux kernel 5.15.190, 6.1.147, 6.12.40, 6.15.8. Check the vendor advisory for mitigations.

References

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