CVE-2026-54271

Home/CVE/protobufjs-cli is the command line add-on for protobuf.js. Prior to 1.3.2 and 2.5.0, a previous fix for unsafe name hand

CVE

↯ PDF report

protobufjs-cli is the command line add-on for protobuf.js. Prior to 1.3.2 and 2.5.0, a previous fix for unsafe name hand

protobufjs-cli is the command line add-on for protobuf.js. Prior to 1.3.2 and 2.5.0, a previous fix for unsafe name handling in pbjs static / static-module code generation was incomplete. Affected versions of protobufjs-cli could still emit unsafe JavaScript references when generating static output from crafted JSON descriptor input.

The common case of parsing schemas from .proto files is not affected. This is a bypass of CVE-2026-44295. An attacker who can provide or influence pre-parsed JSON descriptors passed to pbjs static code generation may be able to cause generated JavaScript output to contain attacker-controlled code.

The injected code may execute if the generated file is later executed or imported and an affected generated API path is invoked. This vulnerability is fixed in 1.3.2 and 2.5.0.

HIGH · CVSS 8.2

Schedule remediation

CVSS base score ≥ 7.0

No Sigma yet — build one → YARA rules0

Look this up elsewhere - one-click external pivots

NVD CVE.org CISA Exploit-DB GitHub PoC VulnCheck KEV GreyNoise

▸ How to read a CVE - triage first, then detect and patch

This page is every public fact about CVE-2026-54271, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.

Triage: should I act now? Four signals, and they are not interchangeable:

CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked. EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal. CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score. Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.

How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.

Then what - two workflows:

Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits. PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.

Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).

▣

Severity & exploitation scoring

View on NVD →

CVSS base score

8.2

HIGHCVSS v3.1 · [email protected]

EPSS exploitation probability

n/a

No EPSS score in our data for this CVE. EPSS is published daily for scored CVEs - a very new, reserved, or rejected CVE may not have one yet.

CVSS metric silhouette

shape grows toward worst-case

SSVC triage

No SSVC vulnrichment for this CVE. CISA's Vulnrichment program scores newer CVEs (~2024 onwards) plus selected older critical ones. Use the EPSS probability + KEV status to triage instead.

CVSS vector breakdown

Exploitability - how they get in

Attack Vector

Network Adjacent Local Physical

Attack Complexity

Low High

Privileges Required

None Low High

User Interaction

None Required

Scope

Unchanged Changed

Impact - what breaks

Confidentiality

None Low High

Integrity

None Low High

Availability

None Low High

VECTORCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:L

Attack path

Full kill chain

→

◆

ATT&CK techniques

Techniques this CVE enables. Pills with a solid outline are high confidence - named directly in ATT&CK or Nuclei, or human-curated by CTID; the rest are inferred from the weakness type using MITRE's CVE Mapping Methodology and the CWE → CAPEC chain. Broad, generic-weakness guesses are filtered out. A small N× marks a technique that N independent sources agree on.

T1027.006 · HTML Smuggling T1027.009 · Embedded Payloads T1059 · Command and Scripting Interpreter T1564.009 · Resource Forking

▤ Build a SIEM detection for these techniques

▤

CAPEC attack patterns

Attack patterns this CVE enables - the bridge from weakness to ATT&CK technique.

CAPEC-CAPEC-242 · Code Injection CAPEC-CAPEC-35 · Leverage Executable Code in Non-Executable Files CAPEC-CAPEC-77 · Manipulating User-Controlled Variables

⬡

Weakness Classification

CWE-94Improper Control of Generation of Code ('Code Injection')

▤

Affected Packages

Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.

npm protobufjs-cli HIGH fixed in 1.3.2

▤

Related CVEs

CVEs linked to this one by a shared weakness (CWE) or affected product - joins on data already in the engine, with the reason shown per row. Not a guess.

CVE-1999-0509 Perl, sh, csh, or other shell interpreters are installed in the cgi-bin director... same CWE-94 CVE-1999-0491 The prompt parsing in bash allows a local user to execute commands as another us... 1 same CWE-94 CVE-1999-0891 The "download behavior" in Internet Explorer 5 allows remote attackers to read a... 1 same CWE-94 CVE-1999-0702 Internet Explorer 5.0 and 5.01 allows remote attackers to modify or execute file... 1 same CWE-94

🔗

References & Sources

Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.

https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-pr59-h9ph-3fr8