CVE-2026-48686: FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI (Network Lay

Q: How do I fix CVE-2026-48686?

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

Q: Is CVE-2026-48686 being exploited?

CVE-2026-48686 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-2026-48686 affect?

CVE-2026-48686 affects fastnetmon. Severity is critical (CVSS 9.8). FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI (Network Layer Reachability Information) decoder. The function decode_bgp_subnet_encoding_ipv4_raw() in src/bgp_protocol.cpp reads prefix_bit_

Q: How urgent is CVE-2026-48686?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-48686 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 a stack-based buffer overflow in the BGP NLRI (Network Layer Reachability Information) decoder. The function decode_bgp_subnet_encoding_ipv4_raw() in src/bgp_protocol.cpp reads prefix_bit_length directly from the BGP packet (line 99) without validating it is <= 32 for IPv4 prefixes. This value is passed to how_much_bytes_we_need_for_storing_certain_subnet_mask() which computes ceil(prefix_bit_le

Why this priority

Critical severity
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	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-120, CWE-787
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 16:16 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.

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-2026-48686?

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

Is CVE-2026-48686 being exploited?

CVE-2026-48686 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-2026-48686 affect?

CVE-2026-48686 affects fastnetmon. Severity is critical (CVSS 9.8). FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI (Network Layer Reachability Information) decoder. The function decode_bgp_subnet_encoding_ipv4_raw() in src/bgp_protocol.cpp reads prefix_bit_

How urgent is CVE-2026-48686?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-48689 CRITICAL 9.8 UPGRADE FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_bi
CVE-2026-48691 CRITICAL 9.8 UPGRADE FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder
CVE-2026-48688 HIGH 7.5 UPGRADE FastNetMon Community Edition through 1.2.9 contains multiple out-of-bounds reads in the BGP MP_REACH_NLRI IPv6
CVE-2026-48684 MEDIUM 6.5 UPGRADE FastNetMon Community Edition through 1.2.9 contains an out-of-bounds read in the NetFlow v9 options template p
CVE-2026-48692 HIGH 8.1 UPGRADE FastNetMon Community Edition through 1.2.9 exposes a gRPC API server on port 50052 with no authentication mech

References

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