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Fencer Vulns
medium 5.9

CVE-2026-49837 json

GoBGP: BGP OPEN capability parser may read capability values outside declared CapLen boundaries

published 2026-07-09 4 mo ago modified 2026-09-16 54 d ago also EUVD-2026-75806 , GHSA-gjrg-jjr3-56cm , GO-2026-5955

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 26%
public exploits
0
none known

Summary

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. Versions prior to 4.6.0 contain a BGP OPEN capability parsing issue where several concrete capability decoders may parse data from the full remaining capability buffer instead of the slice bounded by the declared capability length, `CapLen`. A malformed BGP OPEN message can cause bytes from a following capability to be interpreted as part of the current capability. The most security-relevant case is the 4-octet AS capability, where a capability with `CapLen == 0` may cause the parser to read bytes from the following capability as the 4-octet AS value. This parsed value may later affect peer AS validation during BGP session establishment. Version 4.6.0 patches the issue.

Patch / fix

  • go github.com/osrg/gobgp/v4 4.6.0
  • osrg gobgp 4.6.0
  • gobgp Debian 14 4.6.0-1

debian advisories DEBIAN-CVE-2026-49837

  • govulncheck-vulndb SLES 16.0, SLES for SAP applications 16.0 0.0.20260727T201416-160000.1.1

suse advisories SUSE-SU-2026:23216-1SUSE-SU-2026:23227-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260727T201416-160000.1.1

opensuse advisories openSUSE-SU-2026:21551-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-49837 updated cvss 7.4

github.com/osrg/gobgp: GoBGP: Malformed BGP OPEN message can disrupt BGP sessions

  • Red Hat OpenShift Container Platform 4 openshift4/metallb-rhel8
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
55 d ago

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 26% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
GitHub 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
go github.com/osrg/gobgp/v4
<4.6.0
4.6.0

Affected products

  • osrg gobgp

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.