CVE-2026-33993

CRITICALNVD 9.89.8
EchelonGraph scoreLOW confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: nvd
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 9.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Prior to version 3.0.25, the unserialize() function in locutus/php/var/unserialize assigns deserialized keys to plain objects via bracket notation without filtering the __proto__ key. When a PHP serialized payload contains __proto__ as an array or object key, JavaScript's __proto__ setter is invoked, replacing the deserialized object's prototype with attacker-controlled content. This enables property injection, for...in propagation of injected properties, and denial of service via built-in method override. This is distinct from the previously reported prototype pollution in parse_str (GHSA-f98m-q3hr-p5wq, GHSA-rxrv-835q-v5mh) — unserialize is a different function with no mitigation applied. Version 3.0.25 patches the issue.

CVSS v3
9.8
EG Score
9.8(low)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
—
EPSS %ILE
—
KEV
Not listed

Published

March 27, 2026

Last Modified

June 17, 2026

Advisory Details (4)

Auto-updated Jul 27, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github_release, github.
github Patch Available🟡 PoC Available

Prototype injection via \_\_proto\_\_ key in unserialize() enables property injection and method override on deserialized objects · Advisory · locutusjs/locutus · GitHub

https://github.com/locutusjs/locutus/security/advisories/GHSA-4mph-v827-f877
github_release Patch Available

v3.0.25

Patch available: locutusjs/locutus v3.0.25

https://github.com/locutusjs/locutus/releases/tag/v3.0.25
github_pr Patch Available

fix: harden php prototype pollution sinks

Patch available: locutusjs/locutus v3.0.25 (PR #597 merged 2026-03-25)

https://github.com/locutusjs/locutus/pull/597
github_commit Patch Available

commit 345a6211e1e6 (locutusjs/locutus)

Patch available: locutusjs/locutus v3.0.25 (contains commit 345a6211e1e6)

https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcf9e4

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 1× in last 7d / 1× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-27 14:19 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(4)

What is CVE-2026-33993?
CVE-2026-33993 is a critical vulnerability published on March 27, 2026. Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Prior to version 3.0.25, the unserialize() function in locutus/php/var/unserialize assigns deserialized keys to plain objects via bracket notation without filtering the proto key. When a PHP serialized…
When was CVE-2026-33993 disclosed?
CVE-2026-33993 was first published in the National Vulnerability Database on March 27, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-33993?
CVE-2026-33993 has a CVSS v3 base score of 9.8 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-33993?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33993, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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