CVE-2026-48688
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedFastNetMon Community Edition through 1.2.9 contains multiple out-of-bounds reads in the BGP MP_REACH_NLRI IPv6 attribute decoder. The function decode_mp_reach_ipv6() in src/bgp_protocol.cpp contains a TODO comment at line 156 explicitly acknowledging 'we should add sanity checks to avoid reads after attribute memory block.' The function casts raw pointers to structure types without verifying sufficient data exists (line 158), uses the attacker-controlled length_of_next_hop field to determine memcpy size (line 181), and computes prefix_length by dereferencing a pointer calculated from multiple attacker-controlled offsets without bounds validation (line 189). The prefix_length is then used to calculate number_of_bytes_required_for_prefix which becomes a memcpy length (line 202) with no check against remaining buffer size.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFastNetMon Community Edition 1.2.9 and earlier contains multiple out-of-bounds read vulnerabilities in the BGP MP_REACH_NLRI IPv6 attribute decoder (decode_mp_reach_ipv6()). The function uses attacker-controlled length fields to determine memcpy sizes without validating buffer boundaries, and computes prefix lengths from unvalidated pointer offsets. An attacker sending malformed BGP UPDATE messages with specially crafted MP_REACH_NLRI attributes could trigger out-of-bounds memory reads, potentially leading to information disclosure or denial of service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 1.2.9CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify FastNetMon installation and versionRun command: dpkg -l | grep fastnetmon or rpm -qa | grep -i fastnetmon, or check /opt/fastnetmon/VERSION file if it existsAffected if Version is 1.2.9 or lower
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Confirm BGP processing is enabledInspect FastNetMon configuration file (usually /etc/fastnetmon.conf) for 'bgp_enabled' or 'process_bgp' setting set to 'yes' or 'true'Affected if BGP processing is enabled in configuration
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Verify IPv6 BGP support is activeCheck configuration for 'bgp_ipv6_enabled' or 'enable_ipv6_bgp' set to 'yes', and inspect BGP peer configuration for any IPv6 neighborsAffected if IPv6 support for BGP is enabled and IPv6 peers are configured
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Locate vulnerable decoder functionIf source code is available, examine src/parser/bgp.cpp for decode_mp_reach_ipv6() function around lines 181 and 202 for memcpy using unchecked length fieldsAffected if Source code shows memcpy operations using length_of_next_hop or number_of_bytes_required_for_prefix without bounds validation
System is affected if running FastNetMon Community Edition version 1.2.9 or lower with BGP processing enabled and IPv6 BGP support active, as the vulnerable decode_mp_reach_ipv6() function processes attacker-controlled IPv6 attributes without bounds checking.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedImplement comprehensive bounds validation before all memory operations in decode_mp_reach_ipv6(). Validate that buffer contains sufficient data before pointer casts, verify attacker-controlled length fields against remaining buffer size before use in memcpy operations, and add sanity checks on prefix_length calculations. Consider applying the existing TODO comment at line 156 as a prioritized fix.
Latest stable release newer than 1.2.9 (check GitHub releases for specific version number containing the security fix)
- 1. Identify the current FastNetMon version installed by checking the application or package manager
- 2. Visit the official FastNetMon GitHub repository at github.com to check for releases newer than version 1.2.9
- 3. Review the release notes and changelog for security fixes related to CVE-2026-48688
- 4. Download or upgrade to the latest stable release that includes the fix for the out-of-bounds read vulnerability in decode_mp_reach_ipv6()
- 5. Test the upgrade in a non-production environment to ensure compatibility with existing configurations
- 6. Deploy the updated version to production after successful validation
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,808.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-48688 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-48688 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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