Reachable Assertion Affecting bpftool6.18-debuginfo package, versions <1:6.18.54-121.166.amzn2023


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.17% (6th percentile)

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  • Snyk IDSNYK-AMZN2023-BPFTOOL618DEBUGINFO-21422326
  • published22 Oct 2026
  • disclosed25 Sept 2026

Introduced: 25 Sep 2026

NewCVE-2026-98061  (opens in a new tab)
CWE-617  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 bpftool6.18-debuginfo to version 1:6.18.54-121.166.amzn2023 or higher.
This issue was patched in ALAS2023-2026-3192.

NVD Description

Note: Versions mentioned in the description apply only to the upstream bpftool6.18-debuginfo package and not the bpftool6.18-debuginfo package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

bpf: Reject tail calls directly from callback frames

A tail call from a non-zero frame is modeled as a return from that frame. The verifier makes R0 unknown and calls prepare_func_exit() for the taken branch.

When the current frame is a synchronous callback, prepare_func_exit() enforces the callback return-value contract and marks R0 precise. Since the tail-call path synthesized R0 rather than deriving it from an instruction, precision backtracking reaches the callback-calling instruction with R0 still requested and triggers the "callback unexpected regs" verifier bug. A CAP_BPF task can therefore cause a WARN and an -EFAULT BPF_PROG_LOAD.

Tail calls reachable from callbacks are already rejected later by check_max_stack_depth(). Reject a tail call made directly by a callback before constructing the inconsistent return state, using the existing diagnostic. Tail calls from ordinary subprograms keep their current behavior.

CVSS Base Scores

version 3.1