MEDIUM

CVE-2026-59876

CVSS v3

4.8

MEDIUM

EPSS Score

0.3 %

exploit probability, as of 2026-10-17

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

protobufjsnpmfrom 8.2.0 · fixed in 8.6.5

Vendor advisories

CVE-2026-59876 Red Hat Product Security1 known affected
protobufjs: protobufjs: Prototype pollution vulnerability in Text Format extension
rhceph/alloy-rhel10 as a component of Red Hat Ceph Storage 9

Full record on NVD

Description

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.

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Published: 2026-07-08
Last Modified: 2026-07-08
GitHub Advisory: GHSA-jfj6-75fj-8934

Frequently asked questions

What is CVE-2026-59876?

Is CVE-2026-59876 actively exploited?

Active exploitation of CVE-2026-59876 has not been confirmed. Its EPSS score was 0.3% on 2026-10-17, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-59876?

CVE-2026-59876 has a CVSS v3 base score of 4.8 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.

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