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BusyBox EUVDEUVD-2026-98898

| CVE-2026-88838 MEDIUM
Protection Mechanism Failure (CWE-693)
2026-10-13 secalert@redhat.com GHSA-wq8x-j557-xr3g
5.5
CVSS 3.1 · Vendor: redhat
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain local non-root shell
  2. Delivery
    Invoke BusyBox mount with clearing-mask options
  3. Exploit
    Options bypass non-root flag filter and override fstab nosuid/nodev/noexec
  4. Execution
    Mount crafted filesystem with protections cleared
  5. Impact
    Execute setuid/device payload for privilege escalation

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V15 - Secure Coding and Architecture Protection mechanism completeness
Exploitation Conditions

Requires an interactive local account as a non-root user AND an /etc/fstab configured to let that user mount a device (e.g. a 'user'/'users' entry) while relying on nosuid, nodev, and/or noexec to constrain it, with BusyBox's mount applet as the active mount implementation. Limiting factors: no remote vector, the attacker must already be authenticated locally (PR:L), and systems with no user-mountable fstab entries or with BusyBox mount filtering fixed are not exploitable - this is not a default-configuration remote flaw.

Impact

This is a moderate, locally-scoped privilege/protection-mechanism issue, not an urgent remote threat. The provided CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N, base 5.5) is internally consistent with the description: it requires local access (AV:L) by an already-authenticated low-privileged user (PR:L), is easy to perform once prerequisites exist (AC:L), and affects integrity only (I:H) because it defeats administrator-intended mount hardening (nosuid/nodev/noexec) without directly disclosing data (C:N) or denying service (A:N). No EPSS score, no CISA KEV listing, and no public exploit code were provided in the input, so there is no public exploit identified at time of analysis and no evidence of active exploitation. No SSVC decision data was supplied. The signals are not conflicting but they ARE thin: the only sources are a Red Hat advisory and a Red Hat Bugzilla entry, both marked with no title in the input, and there is no NVD CPE/version data. Net: real but low-to-moderate priority - most dangerous as a local privilege-escalation stepping stone (bypassing noexec/nosuid enables running attacker-controlled setuid binaries) on multi-user systems that explicitly allow non-root mounts.

Exploit ScenarioDerived

A local, low-privileged user on a system where /etc/fstab grants them the ability to mount a device invokes BusyBox mount with clearing-mask options on the command line. These options survive BusyBox's non-root flag filter and, once merged with the fstab options and re-parsed, clear the nosuid/nodev/noexec protections the administrator set - letting the user mount a crafted filesystem and execute setuid or device-backed payloads for local privilege escalation. No public exploit code was identified in the provided data, and exploitation requires prior local account access (AV:L/PR:L).

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 13, 2026

Local, authenticated non-root users can bypass nosuid, nodev, and noexec mount restrictions enforced via /etc/fstab in BusyBox's mount utility by supplying clearing-mask options on the command line, potentially leading to integrity violations such as executing setuid programs or device access. The flaw requires a specific configuration where an fstab entry permits the user to mount a device and relies on those protections; it is not remotely exploitable. No public exploit code or active exploitation has been identified at time of analysis, and the EPSS score is not provided.

RemediationAI

No specific patch version is identified in the available data; apply the vendor-released update from Red Hat or upstream BusyBox once available. As an immediate mitigation, remove the 'user' or 'users' option from /etc/fstab entries that depend on nosuid, nodev, or noexec to restrict non-root mounts, or replace BusyBox mount with the util-linux mount implementation. Note that removing user-mountable entries may disrupt legitimate workflows. Additionally, audit fstab for any user-mountable filesystems and consider tightening permissions. Monitor the Red Hat advisory (https://access.redhat.com/security/cve/CVE-2026-88838) and Bugzilla (https://bugzilla.redhat.com/show_bug.cgi?id=2531352) for patch availability.

Affected ProductsAI

BusyBox's mount utility is affected. The vulnerability impacts systems where BusyBox mount is the active mount implementation and /etc/fstab contains entries with the 'user' or 'users' option that rely on nosuid, nodev, or noexec for security. No specific version range is provided in the available data; refer to the Red Hat advisory (https://access.redhat.com/security/cve/CVE-2026-88838) and Bugzilla (https://bugzilla.redhat.com/show_bug.cgi?id=2531352) for version details. CPE information is not provided.

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Technical ContextAI · show details

The vulnerability resides in BusyBox's mount applet, a compact implementation commonly used in embedded systems and minimal containers. CWE-693 (Protection Mechanism Failure) describes the root cause: the mount utility fails to properly filter clearing-mask options (e.g., 'suid', 'dev', 'exec') when a non-root user invokes mount on an fstab entry that allows user mounting. The options supplied by the user are merged with fstab options as strings and then re-parsed, allowing the clearing options to override the administrator's intended nosuid, nodev, and noexec restrictions. This defeats the security hardening configured in /etc/fstab. The issue is local and requires an authenticated user with a pre-existing user-mountable fstab entry, as reflected in the CVSS vector (AV:L/PR:L).

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Severity by source

Vendor (redhat) PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
vuln.today AI 5.5 MEDIUM

Local non-root user (AV:L/PR:L) trivially passes options (AC:L) to defeat mount hardening, giving high integrity impact only (I:H), with no data disclosure or DoS.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Red Hat 5.5 MEDIUM

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

DescriptionCVE.org

A flaw was found in BusyBox's mount utility. A non-root user can bypass mount security restrictions set in /etc/fstab by specifying clearing-mask options on the command line. These options pass the non-root flag filter and are merged with fstab options as strings; when the combined options are re-parsed, clearing options can override nosuid, nodev, and noexec protections the administrator intended to enforce.

Threat Intelligence Overview

EPSS Score
0.1%
Top 99% exploitable
Prevalence
Ubiquitous
BusyBox is standard in most embedded Linux, routers, and container images
Social Media
2
Sightings
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.1%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Defer
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

28
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

CVE-2016-2148 CRITICAL POC
9.8 Feb 09

Heap-based buffer overflow in the DHCP client (udhcpc) in BusyBox before 1.25.0 allows remote attackers to have unspecif

CVE-2017-16544 HIGH POC
8.8 Nov 20

In the add_match function in libbb/lineedit.c in BusyBox through 1.27.2, the tab autocomplete feature of the shell, used

CVE-2016-2147 HIGH POC
7.5 Feb 09

Integer overflow in the DHCP client (udhcpc) in BusyBox before 1.25.0 allows remote attackers to cause a denial of servi

CVE-2022-28391 HIGH POC
8.8 Apr 03

BusyBox through 1.35.0 allows remote attackers to execute arbitrary code if netstat is used to print a DNS PTR record's

CVE-2025-60876 MEDIUM POC
6.5 Nov 10

BusyBox wget thru 1.3.7 accepted raw CR (0x0D)/LF (0x0A) and other C0 control bytes in the HTTP request-target (path/que

CVE-2022-30065 HIGH POC
7.8 May 18

A use-after-free in Busybox 1.35-x's awk applet leads to denial of service and possibly code execution when processing a

CVE-2019-5747 HIGH POC
7.5 Jan 09

An issue was discovered in BusyBox through 1.30.0. Rated high severity (CVSS 7.5), this vulnerability is remotely exploi

CVE-2013-1813 HIGH POC
7.2 Nov 23

util-linux/mdev.c in BusyBox before 1.21.0 uses 0777 permissions for parent directories when creating nested directories

CVE-2025-12220 CRITICAL
10.0 Oct 25

Network-reachable BLU-IC2 and BLU-IC4 devices running firmware through 1.19.5 embed BusyBox 1.31.1 and are exposed to mu

CVE-2021-42377 CRITICAL
9.8 Nov 15

An attacker-controlled pointer free in Busybox's hush applet leads to denial of service and possible code execution when

CVE-2018-1000517 CRITICAL
9.8 Jun 26

BusyBox project BusyBox wget version prior to commit 8e2174e9bd836e53c8b9c6e00d1bc6e2a718686e contains a Buffer Overflow

CVE-2023-42366 MEDIUM POC
5.5 Nov 27

A heap-buffer-overflow was discovered in BusyBox v.1.36.1 in the next_token function at awk.c:1159. Rated medium severit

Vendor StatusVendor

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