Monitoring Plugins check_icmp: -H argument count overflow leads in setuid-root binary
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 3.0.1
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Affected versions 3.0.0-rc1 through 3.0.0 of check_icmp More than 65535 hosts supplied via -H/--Host, or via Host= entries in --extra-opts files check_icmp installed setuid-root for the privilege escalation consequence
- Exploitation0/40No signal
- Exposure5/25Specific setups only
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity8/10CVSS 7.0, total technical impact per CISA
- No patch0/5No signal
What would change the score
- Would score about 63 if added to CISA KEV
- Would score about 58 if CISA's SSVC rates exploitation active
- Would score about 23 if CISA's SSVC rates it automatable
CVE-2026-63418 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.0 (high) and affects monitoring-plugins; fixed in 3.0.1.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 13/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Fix
- Fixed in 3.0.1
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: total
Summary
Monitoring Plugins' check_icmp plugin is affected, particularly on installations where it is setuid root. A local, low-privileged user supplying more than 65,535 hosts can overflow a counter and corrupt heap memory while the process still runs with root privileges, which could potentially lead to privilege escalation, though this has not been demonstrated.
Read the original description
Monitoring Plugins is a suite of plugins for monitoring applications. From 3.0.0-rc1 until 3.0.1, check_icmp stores the number of hosts supplied through -H or --Host on the command line, or through --extra-opts files containing Host= entries, in an unsigned short. More than 65,535 hosts wrap the counter, causing process_arguments() to allocate an undersized hosts array and then write subsequent entries out of bounds before main() calls setuid(getuid()). On installations where check_icmp is setuid root, a local low-privileged attacker can corrupt heap memory while the process still has root privileges; reliable privilege escalation has not been demonstrated. Installations that use cap_net_raw file capabilities instead of setuid are not exposed to the privilege-escalation consequence. This issue is fixed in version 3.0.1.
What to do
Check whether your setup matches what the bug needs.
Affected versions 3.0.0-rc1 through 3.0.0 of check_icmp More than 65535 hosts supplied via -H/--Host, or via Host= entries in --extra-opts files check_icmp installed setuid-root for the privilege escalation consequenceUpgrade to a fixed version: 3.0.1.
Workaround: Use file capabilities (cap_net_raw) instead of the setuid bit
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- monitoring-plugins monitoring-plugins
From 3.0.0-rc1 · fixed in 3.0.1
Evidence 3
- Advisory
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-63418
Is CVE-2026-63418 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
check_icmp counts the hosts it is given with a counter that wraps when there are more than 65535 of them, which corrupts heap memory. The bug is a local heap buffer overflow in a process that still runs as root, and it may allow privilege escalation, though reliable escalation has not been demonstrated.Source: github.com
Which versions are affected by CVE-2026-63418?
monitoring-plugins: from 3.0.0-rc1 before 3.0.1.Source: cve.now feed data
Am I affected, and how do I check?
Versions 3.0.0-rc1 through 3.0.0 of check_icmp are affected, and the problem needs more than 65535 hosts given via -H/--Host or Host= entries in --extra-opts files. The escalation consequence applies where check_icmp is installed setuid-root, as confirmed on Arch Linux's monitoring-plugins package; check the installed version with check_icmp --version and whether the binary has the setuid bit set with ls -l on its path.Source: github.com
How do I fix CVE-2026-63418?
Upgrade to Monitoring Plugins 3.0.1 or later, which contains the fix.Source: github.com