Cyber Resilience

CVE-2026-59876

Protobufjs Project Protobufjs 8.2.0 – 8.6.5

Published
08 July 2026
Modified
13 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 4.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS Score 0.0022 13th percentile
Risk Priority 38 floored blend · peak EPSS

Summary

CVE-2026-59876 is a medium-severity Prototype Pollution (CWE-1321) vulnerability in Protobufjs Project Protobufjs. Its CVSS base score is 4.8 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 13th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability Data

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…

more

object instead of creating an own map entry in protobufjs/ext/textformat. This issue is fixed in version 8.6.5.

CWE(s)
CWE-1321

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1565 Data Manipulation Impact
Adversaries may insert, delete, or manipulate data in order to influence external outcomes or hide activity, thus threatening the integrity of the data.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-44290Same product: Protobufjs Project Protobufjs
CVE-2026-44292Same product: Protobufjs Project Protobufjs
CVE-2023-36665Same product: Protobufjs Project Protobufjs
CVE-2026-44294Same product: Protobufjs Project Protobufjs
CVE-2026-41242Same product: Protobufjs Project Protobufjs
CVE-2026-44293Same product: Protobufjs Project Protobufjs
CVE-2026-44291Same product: Protobufjs Project Protobufjs
CVE-2026-44288Same product: Protobufjs Project Protobufjs
CVE-2026-44289Same product: Protobufjs Project Protobufjs
CVE-2026-48712Same product: Protobufjs Project Protobufjs

Affected Assets

protobufjs project
protobufjs
8.2.0 — 8.6.5

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V15.3.6

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and safe property assignment to prevent prototype pollution.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development catches prototype-pollution flaws before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and object-handling controls that directly prevent prototype pollution.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for safeguards against unsafe object attribute manipulation.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles reduce the likelihood of prototype pollution through safe design patterns.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prohibit unsafe prototype attribute assignment and require defensive checks.

A.8.32 Change management partial match
prevents

Change-management processes ensure security fixes for prototype-pollution issues are tracked and deployed.

References