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Fencer Vulns
medium 4.8

CVE-2026-59876 json

protobufjs: Text Format string map parsing can mutate returned map object prototype

published 2026-07-08 4 mo ago modified 2026-10-25 14 d ago also GHSA-jfj6-75fj-8934 , EUVD-2026-42311

cvss
4.8
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 28%
public exploits
0
none known

Summary

protobufjs compiles protobuf definitions into JavaScript (JS) functions. From 8.2.0 until 8.6.5, the protobufjs Text Format extension parsed string-keyed map entries using ordinary property assignment, allowing a map entry with key __proto__ to change the prototype of the returned map object instead of creating an own map entry in protobufjs/ext/textformat. This issue is fixed in version 8.6.5.

Patch / fix

  • npm protobufjs 8.6.5
  • protobufjs_project protobufjs 8.6.5

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-2026-59876 updated cvss 4.8

protobufjs: protobufjs: Prototype pollution vulnerability in Text Format extension

  • Red Hat Ceph Storage 9 rhceph/alloy-rhel10
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Cryostat 4 grafana-infinity-datasource-npm Red Hat OpenShift Pipelines openshift-pipelines/pipelines-console-plugin-rhel8, openshift-pipelines/pipelines-console-plugin-rhel9, openshift-pipelines/pipelines-console-plugin-pf5-rhel9 Red Hat OpenShift Service Mesh 3 openshift-service-mesh/kiali-rhel9, openshift-service-mesh/kiali-ossmc-rhel9 Red Hat Ansible Automation Platform 2 automation-platform-ui 2.6.10-1.el9ap, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-27/gateway-rhel9 Red Hat Build of Podman Desktop rh-podman-desktop.git Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9
    +2 more products
    Red Hat Enterprise Linux 8 grafana, grafana-loki, grafana-mssql, grafana-mysql, grafana-selinux, grafana-graphite, +8 more Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/disk-image-cuda-rhel9
    not affected: vulnerable code not present
  • Red Hat Hardened Images dotnet9.0 9.0.118-1.hum1
    not affected: component not present
  • Red Hat OpenShift Container Platform 4 openshift4/ose-console, openshift4/ose-console-rhel9 Red Hat OpenShift Container Platform 5 openshift5/ose-console-rhel9 Red Hat Openshift Data Foundation 4 odf4/mcg-core-rhel9 Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal, ansible-automation-platform/bootc-automation-portal-rhel9
    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
4 mo ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
NVD 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
GitHub 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm protobufjs
>=8.2.0, <8.6.5
8.6.5

Affected products

  • protobufjs protobuf.js

Classification

Weakness
  • CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

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.