Cyber Resilience

CVE-2026-33151

Socket.Io-Parser ≤ 3.3.5

Published
20 March 2026
Modified
14 April 2026
Patch / advisory
View advisory
CVSS Score v4 8.7
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0051 41th percentile
Risk Priority 45 floored blend · peak EPSS

Summary

CVE-2026-33151 is a high-severity Improper Input Validation (CWE-20) vulnerability in Socket Socket.Io-Parser. Its CVSS base score is 8.7 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 41th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-33151 is a denial-of-service vulnerability in Socket.IO, an open-source real-time, bidirectional, event-based communication framework. In versions prior to 3.3.5, 3.4.4, and 4.2.6, a specially crafted Socket.IO packet can cause the server to wait indefinitely for a large number of binary attachments, leading it to buffer excessive data and exhaust available memory. The vulnerability is rated with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is associated with CWE-20 (Improper Input Validation) and CWE-754 (Improper Check for Unusual or Exceptional Conditions).

Unauthenticated attackers with network access can exploit this issue with low complexity and no user interaction required. By sending the malicious packet, they trigger the server to allocate memory for numerous expected attachments that never arrive, resulting in resource exhaustion and potential service disruption or crash.

The vulnerability has been addressed in Socket.IO versions 3.3.5, 3.4.4, and 4.2.6, with fixes detailed in GitHub commits such as 719f9ebab0772ffb882bd614b387e585c1aa75d4, 9d39f1f080510f036782f2177fac701cc041faaf, and b25738c416c4e32fbff62ee182afa8f6d0dacf78, as well as the GHSA-677m-j7p3-52f9 security advisory. Security practitioners should upgrade affected Socket.IO installations to these patched versions to mitigate the risk.

OWASP Top 10 for Web (2025)

A05:2025 InjectionA10:2025 Mishandling of Exceptional Conditions

EU & UK References

Vulnerability Data

Socket.IO is an open source, real-time, bidirectional, event-based, communication framework. Prior to versions 3.3.5, 3.4.4, and 4.2.6, a specially crafted Socket.IO packet can make the server wait for a large number of binary attachments and buffer them, which can be…

more

exploited to make the server run out of memory. This issue has been patched in versions 3.3.5, 3.4.4, and 4.2.6.

CWE(s)
CWE-20CWE-754NVD-CWE-noinfo

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 →
T1489 Service Stop Impact
Adversaries may stop or disable services on a system to render those services unavailable to legitimate users.
attack.mitre.org →
T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1036.001 Invalid Code Signature Stealth
Adversaries may attempt to mimic features of valid code signatures to increase the chance of deceiving a user, analyst, or tool.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-32695Same product: Socket Socket.Io-Parser
CVE-2026-59724Same vendor: Socket
CVE-2026-45678Shared CWE-20, CWE-754
CVE-2024-38355Shared CWE-20, CWE-754
CVE-2026-69185Shared CWE-20, CWE-754
CVE-2025-69250Shared CWE-20, CWE-754
CVE-2026-59725Same vendor: Socket
CVE-2023-31125Same vendor: Socket
CVE-2026-34066Shared CWE-20, CWE-754
CVE-2026-21693Shared CWE-20, CWE-754

Affected Assets

socket
socket.io-parser
≤ 3.3.5 · 3.4.0 — 3.4.4 · 4.0.0 — 4.2.6

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 13 hardening rules · 4 OS baselines
Validate
Prove the fix (OWASP ASVS)

—

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover missing input validation through analysis or test cases.

SI-10 Information Input Validation good match

SI-10 directly requires validity checks on information inputs, structurally preventing improper or missing validation.

SA-15 Development Process, Standards, and Tools partial match

Requiring documented development standards and tools can embed input-validation practices into the engineering process.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles include structured handling of edge cases and exceptions during design.

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 and enforce input validation during development.

DE.CM-09 partial match
prevents

Runtime monitoring of software and environments can detect adverse events triggered by unhandled exceptional conditions.

PR.PS-04 partial match
prevents

Generating logs of exceptions and errors enables detection of improper handling of unusual conditions.

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

Testing against a defined set of requirements and using code review plus vulnerability scanning forces validation of inputs and handling of unanticipated conditions, reducing the chance that malformed data will be accepted.

A.8.15 Logging partial match
finds

Logging can record unhandled exceptions but does not prevent the weakness itself.

A.8.16 Monitoring activities partial match
finds

Monitoring may detect symptoms of unhandled conditions but does not eliminate the root weakness.

A.8.25 Secure development life cycle partial match
prevents

Secure-coding guidelines and mandatory security testing (including code scans) compel developers to validate and sanitize inputs at design and implementation time, lowering the incidence of malformed or malicious data reaching downstream components.

A.8.26 Application security requirements partial match
prevents

Mandating input controls that include integrity checks and input validation ensures that untrusted data is examined before use, blocking the root cause of many injection and malformed-data weaknesses.

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

Security-by-design principles explicitly call for data validation and sanitization at every layer, reducing the chance that malformed or malicious input will be processed without scrutiny.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (2 rules)
  • V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-754
  • V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-754
Oracle Linux 9 (1 rule)
  • V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. prevents CWE-754
RHEL 8 (1 rule)
  • V-230265 RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-20

References