How severe is CVE-2026-59876?

CVE-2026-59876 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-59876 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (13th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-59876?

CVE-2026-59876 affects Protobufjs Project Protobufjs. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-59876?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-59876 published?

CVE-2026-59876 was published on 2026-07-08 and last updated on 2026-07-13.

CVE-2026-59876

CVE-2026-59876 is a medium-severity vulnerability in Protobufjs Project Protobufjs with a CVSS 3.x base score of 4.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1321.

Key facts

Severity: Medium (CVSS 3.x base score 4.8)
EPSS exploit prediction: 0% (13th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1321
Affected product: Protobufjs Project Protobufjs
Published: 2026-07-08
Last modified: 2026-07-13

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.

Frequently asked questions

What is CVE-2026-59876?: 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.
How severe is CVE-2026-59876?: CVE-2026-59876 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-59876 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (13th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-59876?: CVE-2026-59876 affects Protobufjs Project Protobufjs. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-59876?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-59876 published?: CVE-2026-59876 was published on 2026-07-08 and last updated on 2026-07-13.

References

Affected products (1)

cpe:2.3:a:protobufjs_project:protobufjs:*:*:*:*:*:node.js:*:*

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