Cloudanix VulnDB

CVE-2026-68186

None

CVSS

—

EPSS

0.2%

Published

Aug 10, 2026

CISA due date

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Cloudanix analysis

Next patch cycle SSVC: Track

A mistake in how the operating system handles certain program formats can let ordinary users crash the whole machine by tricking it into running the wrong code at the wrong time.

Exploitation
Local Privilege
Attacker needs
Low Privilege
Complexity
Low
Impact
Denial Of Service
Component
OS kernel
Class
Memory Corruption
Remediation
Patch
Effort
Medium
Patch risk
Low

What it actually does

NULL pointer dereference in begin_new_exec when bprm->executable is NULL but have_execfd flag remains set after binfmt_misc interpreter open fails with -ENOEXEC, causing fallback execution of the original binary.

Why it matters to the business

Unprivileged local users can trigger kernel crashes leading to denial of service; in container or user-namespace environments this may enable broader availability or stability issues across shared systems.

How an attack unfolds

An attacker mounts binfmt_misc inside a user namespace, registers an entry with the O flag whose interpreter resides on a FUSE filesystem that returns -ENOEXEC, then executes a matching native binary; the premature have_execfd flag combined with the absent executable pointer triggers the dereference during exec hand-off.

How to fix it

Apply the upstream kernel commit that moves the have_execfd assignment to occur only after the interpreter has been successfully opened and staged; rebuild and deploy the patched kernel across all affected systems.

How to confirm the fix worked

Confirm the source change that sets have_execfd immediately after a successful interpreter open and next to execfd_creds; recompile, boot the new kernel, and verify that a deliberately failing interpreter open no longer produces a NULL dereference on fallback exec.

Typical attack path

  1. Mount binfmt_misc in a user namespace
  2. Register a misc format entry using the O flag pointing to an interpreter on a controllable FUSE mount
  3. Execute a native binary whose header matches the registered entry
  4. Force the FUSE interpreter open to fail with -ENOEXEC so the search falls through
  5. Trigger the inconsistent bprm state that dereferences a NULL executable pointer

How to detect it

Review kernel logs for oops or panic messages containing load_misc_binary, have_execfd, or begin_new_exec NULL dereferences; correlate with user-namespace mounts of binfmt_misc and FUSE activity immediately preceding the crash.

What your security team should do

  • Prioritize kernel updates on any system exposing binfmt_misc to untrusted users or containers
  • Restrict binfmt_misc mounts inside user namespaces where operationally feasible
  • Monitor kernel oops and panic logs for patterns involving load_misc_binary and begin_new_exec

The record

In the Linux kernel, the following vulnerability has been resolved: binfmt_misc: set have_execfd only once the interpreter is opened load_misc_binary() raises bprm->have_execfd as soon as it sees the 'O' (or 'C') flag. This happens well before it opens the interpreter. If that open fails the flag stays set on the bprm. binfmt_misc is at the head of the format list so an interpreter open failure that returns -ENOEXEC lets the search fall through to a later format. This means it runs the matched binary directly having never staged an interpreter. So bprm->executable is NULL while have_execfd falsely claims a descriptor is present. Consequently, begin_new_exec() dereferences the missing executable: would_dump(bprm, bprm->executable); and NULL derefs. Had it not, the hand-off later in the same function would have failed anyway. FD_ADD(0, bprm->executable) rejects a NULL file with -ENOMEM. Both sites are past the point of no return so the exec cannot be unwound either way. This can be reached by unprivileged users as binfmt_misc can be mounted in user namespaces. So a user can register an 'O' entry whose interpreter lives on a FUSE mount, have the FUSE server fail the open with -ENOEXEC and execute a native ELF file that matches the entry. have_execfd only means anything alongside the executable it describes which is not set until the interpreter has been opened and staged. So lets raise it there, next to execfd_creds, which is already set at that point. An open failure now leaves it clear, so the fallback format derives credentials from the binary and emits no AT_EXECFD, as it would for any native exec. The argv rewrite load_misc_binary() performs before the open is still not undone. This means the binary sees the interpreter path in argv[0] and its own path in argv[1] but that predates this change and only became observable once the exec stopped faulting.

Affected packages

Ecosystem Package Introduced Fixed