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NVD / CVE Program· CNA GitHub_M

CVE-2026-59876: protobufjs: Text Format string map parsing can mutate returned map object prototype

Noroxi assessment

Priority: Monitor (action score 19/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.34% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: protobufjs protobuf.js 8.6.5.

Low priority for now. Upgrade to protobufjs protobuf.js 8.6.5 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 4.8 · v3.1—No exploit Fix available
Published
Jul 8, 2026
Updated
Oct 25, 2026
EPSS
0.3% · 28th percentile

Report tools

JSON

Action score

19

Monitor

Low priority for now.

CVSS
19 / 40 · 4.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
4.8
CNA · GitHub_M
4.8
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
protobufjs projectprotobufjs

Is the protobufjs on your site affected?

The free JavaScript library scanner reads the protobufjs version from the files your site loads, matches this record and other known vulnerabilities, and gives the safe version on the same branch. If the version can't be read, it says so. No account needed.

Scan JavaScript libraries

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • protobufjs project protobufjs8.2.0 and later · before 8.6.5

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • protobufjs protobuf.js

    • >= 8.2.0, < 8.6.5affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
npmprotobufjsfrom 8.2.0 · before 8.6.58.6.5

Same product

protobufjs project: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-36665"protobuf.js (aka protobufjs) 6.10.0 through 7.x before 7.2.5 allows Prototype Pollution, a different vulnerability than CVE-2022-25878.
    40Plan
  • CVE-2026-41242protobufjs has an arbitrary code execution issue
    37Monitor
  • CVE-2026-44291protobufjs: Code generation gadget after prototype pollution
    32Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-54269Jun 22, 2026 · protobufjs: Schema-derived names can shadow runtime-significant properties
    21Monitor
  • ← EarlierCVE-2026-54270Jun 22, 2026 · protobufjs: Memory amplification from preserved unknown fields in binary decode
    21Monitor
  • Later →CVE-2026-59877Jul 8, 2026 · protobufjs: Denial of Service via infinite loop in .proto option parsing
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
protobufjs protobuf.js8.6.5 · descriptionVendor (CNA)
npm:protobufjs8.6.5Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-4429056 days apartprotobufjs: Process-wide denial of service through unsafe option paths
    30Monitor
  • CVE-2026-4429256 days apartprotobufjs: Prototype injection in generated message constructors
    21Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-1321 · Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

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References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records