CVE-2026-5123Network attack vector

Service interruption via off-by-one capability decoding

Published Mar 30, 2026 · Updated Mar 30, 2026

Off-by-one error in GoBGP 4.0 through 4.3.0 allows remote attackers to interrupt service via a crafted BGP software-version capability. CapSoftwareVersion.DecodeFromBytes reads the declared string from data[1:SoftwareVersionLen], omitting its final byte instead of ending at 1+SoftwareVersionLen. Reachability requires a BGP peer to deliver the capability during OPEN processing; published evidence reports only low availability impact and does not identify a specific crash or hang.

CVSS severity6.3
Medium
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Off-by-one error in GoBGP 4.0 through 4.3.0 allows remote attackers to interrupt service via a crafted BGP software-version capability. CapSoftwareVersion.DecodeFromBytes reads the declared string from data[1:SoftwareVersionLen], omitting its final byte instead of ending at 1+SoftwareVersionLen. Reachability requires a BGP peer to deliver the capability during OPEN processing; published evidence reports only low availability impact and does not identify a specific crash or hang.

The record

CVE
CVE-2026-5123
Published
Mar 30, 2026
Updated
Mar 30, 2026
Vendor
GoBGP
Product
GoBGP
Classifications
CWE-193, CWE-189, T1499.004
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

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:N/VA:L/SC:N/SI:N/SA:N
3.7VulDBCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
2.6VulDBAV:N/AC:H/Au:N/C:N/I:N/A:P

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-193Off-by-one Error
CWE-189Numeric Errors
T1499.004Application or System Exploitation

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo