CVE-2026-48689: FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_bi

Q: How do I fix CVE-2026-48689?

fastnetmon: upgrade to newer than 1.2.9. Exact commands for each OS are on this page.

Q: Is CVE-2026-48689 being exploited?

CVE-2026-48689 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-48689 affect?

CVE-2026-48689 affects fastnetmon. Severity is critical (CVSS 9.8). FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_o

Q: How urgent is CVE-2026-48689?

Priority 60/100. Critical severity; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-48689 is a critical-severity flaw (CVSS 9.8) affecting fastnetmon. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_object_ptr, memcpy_from_ptr, memcpy_from_object_ptr) use an incorrect bounds check of the form 'if (offset + length > maximum_internal_storage_size + 1)' instead of the correct 'if (offset + length > maximum_int

Why this priority

Critical severity
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 48%)
CISA exploited list	No
Weakness	CWE-787, CWE-122, CWE-193
Published	2026-05-26
Last modified	2026-07-24

Publisher (CNA): MITRE · Vendor: pavel-odintsov

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-26 19:16 UTCPublished CVE record published
2026-07-24 11:10 UTCUpdated Record last modified

pavel-odintsov fastnetmon UPGRADE

Affected: <= 1.2.9

Fixed in: newer than 1.2.9

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy fastnetmon || rpm -q fastnetmon || fastnetmon --version

2. UPGRADE to newer than 1.2.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade fastnetmon

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fastnetmon

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

Fedora 46 · proftpd · FIXED · 1.3.9e-1.fc46 · FEDORA-2026-fc0d87d66e · source

sudo dnf upgrade --advisory=FEDORA-2026-fc0d87d66e

Ubuntu 20.04 · fastnetmon · NOT AFFECTED

Ubuntu 24.04 · fastnetmon · FIXED · 1.2.6-1ubuntu0.1~esm1

sudo apt update && sudo apt install --only-upgrade fastnetmon dpkg --compare-versions "$(dpkg-query -W -f='${Version}' fastnetmon)" ge "1.2.6-1ubuntu0.1~esm1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · fastnetmon · NOT AFFECTED

Debian 13 · fastnetmon · FIXED · 1.2.9-0+deb13u1

sudo apt update && sudo apt install --only-upgrade fastnetmon dpkg --compare-versions "$(dpkg-query -W -f='${Version}' fastnetmon)" ge "1.2.9-0+deb13u1" && echo PATCHED || echo STILL-VULNERABLE

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-48689?

fastnetmon: upgrade to newer than 1.2.9. Exact commands for each OS are on this page.

Is CVE-2026-48689 being exploited?

CVE-2026-48689 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-48689 affect?

CVE-2026-48689 affects fastnetmon. Severity is critical (CVSS 9.8). FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_o

How urgent is CVE-2026-48689?

Priority 60/100. Critical severity; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Related CVEs

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References

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