Medium [CVE-2026-59876] Prototype pollution vulnerability in Text Format extension
This medium-severity Red Hat Linux advisory covers CVE-2026-59876.
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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. A flaw was found in protobufjs.
An attacker could exploit this to alter object behavior, potentially leading to information disclosure or other impacts. This Moderate-impact flaw in protobufjs allows an attacker to perform prototype pollution by providing specially crafted input to the Text Format extension.
Red Hat severity: Moderate — CVSS 4.8 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N). Weakness: CWE-915.
Under investigation: Cryostat 4; Red Hat Ansible Automation Platform 2; Red Hat Build of Podman Desktop; Red Hat Ceph Storage 9; Red Hat Enterprise Linux 8; Red Hat Openshift Data Foundation 4.
Red Hat lists OpenShift Pipelines; OpenShift Service Mesh 3; Red Hat Developer Hub; Red Hat Enterprise Linux AI (RHEL AI) 3; Red Hat Hardened Images; Red Hat OpenShift Container Platform 4; Self-service automation portal 2 as not affected.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
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