Is CVE-2026-59877 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-59877 being exploited in the wild.

How severe is CVE-2026-59877?

Medium severity, with a CVSS score of 5.3, published 8 July 2026.

Which products and versions are affected?

protobufjs (npm) SEMVER:introduced=7.5.0,fixed=7.6.5.

Is there a fix for CVE-2026-59877?

Yes. protobufjs (npm): upgrade to 7.6.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-59877 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-59877?

Check whether you run protobufjs (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-59877: protobufjs infinite loop in .proto option parsing

CVE-2026-59877 · Severity: medium · CVSS 5.3 · Published 2026-07-08

A vulnerability in the protobufjs library can allow an attacker to crash or freeze a Node.js application. By providing a specially crafted schema file, an attacker can trigger an infinite loop during the parsing process. Because Node.js handles tasks one at a time, this loop blocks all other operations, leading to a complete service outage until the application is manually restarted.

Technologies: protobufjs (npm). Vendors: npm.

Quick answers

Is CVE-2026-59877 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-59877 being exploited in the wild.
How severe is CVE-2026-59877?: Medium severity, with a CVSS score of 5.3, published 8 July 2026.
Which products and versions are affected?: protobufjs (npm) SEMVER:introduced=7.5.0,fixed=7.6.5.
Is there a fix for CVE-2026-59877?: Yes. protobufjs (npm): upgrade to 7.6.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-59877 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-59877?: Check whether you run protobufjs (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

protobufjs (npm): upgrade to 7.6.5 or later
```
npm install protobufjs@7.6.5
```

Technical details

An infinite loop vulnerability exists in protobufjs (CWE-835) within the reflection parsing path, specifically affecting the 'parse', 'Root.load', and 'Root.loadSync' methods. The root cause is the option parser's failure to check for the end of input while searching for an assignment operator ('=') in a .proto schema. An attacker can exploit this by providing a crafted schema that initiates an option declaration but terminates prematurely. In single-threaded Node.js environments, this results in a blocked event loop and a persistent Denial of Service. The issue is resolved in versions 7.6.5 and 8.6.6.

Affected products

protobufjs protobufjs >= 7.5.0, <= 7.6.4
protobufjs protobufjs >= 8.0.0, <= 8.6.5

Identifiers

CVE-2026-59877
GHSA-j3f2-48v5-ccww

Timeline

2026-07-04: disclosed: Vulnerability reported to the maintainer
2026-07-08: advisory: NVD publication date
2026-07-20: advisory: GitHub Advisory published

References

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