CVE-2026-5124Network attack vector

Malformed BGP messages accepted via unchecked marker

Published Mar 30, 2026 · Updated Mar 30, 2026

BGP header validation failure in OSRG GoBGP 4.0 through 4.3.0 allows remote attackers to submit messages with an invalid marker. BGPHeader.DecodeFromBytes accepts a 16-byte Marker that is not all 0xFF rather than returning the required Connection Not Synchronized error. Reachability requires a network path to the BGP listener; upstream disputes any security impact beyond acceptance of a noncompliant header.

CVSS severity6.3
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

BGP header validation failure in OSRG GoBGP 4.0 through 4.3.0 allows remote attackers to submit messages with an invalid marker. BGPHeader.DecodeFromBytes accepts a 16-byte Marker that is not all 0xFF rather than returning the required Connection Not Synchronized error. Reachability requires a network path to the BGP listener; upstream disputes any security impact beyond acceptance of a noncompliant header.

The record

CVE
CVE-2026-5124
Published
Mar 30, 2026
Updated
Mar 30, 2026
Vendor
GoBGP
Product
GoBGP
Classifications
CWE-266, CWE-284
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 30, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.0
  2. Affected versionversion=4.1
  3. Affected versionversion=4.2
  4. Affected versionversion=4.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

GoBGP · GoBGPversion=4.0; version=4.1; version=4.2; version=4.3.0

Published CVSS scores

6.3VulDBCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X
2.6VulDBAV:N/AC:H/Au:N/C:N/I:P/A:N/E:ND/RL:OF/RC:C
3.7VulDBCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:X/RL:O/RC:C
3.7VulDBCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:X/RL:O/RC:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-266Incorrect Privilege Assignment
CWE-284Improper Access Control

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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