---
id: CVE-2026-88355
title: >-
  An incorrect buffer size calculation vulnerability exists in tinyexpr commit
  4a7456e in new_expr()
summary: >-
  An incorrect buffer size calculation vulnerability exists in tinyexpr commit
  4a7456e in new_expr(). For arity-0 expression nodes, including constants,
  variables, and zero-argument functions, the function allocates less memory
  than sizeof…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-131
published: '2026-09-24'
updated: '2026-10-06'
sourceUpdated: '2026-10-06T18:16:57.013'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88355'
references:
  - url: 'https://github.com/codeplea/tinyexpr/issues/145'
    label: cve@mitre.org
  - url: >-
      https://github.com/szaydel/tinyexpr/commit/fe7459728c2ab8d2f91365abe56601cdd0e24f9b
    label: cve@mitre.org
  - url: 'https://github.com/codeplea/tinyexpr/issues/145'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.00415
epssPercentile: 0.3561
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-06T15:44:34.584065Z'
ingestedAt: '2026-09-24T15:45:56.663Z'
---

## Overview

An incorrect buffer size calculation vulnerability exists in tinyexpr commit 4a7456e in new_expr(). For arity-0 expression nodes, including constants, variables, and zero-argument functions, the function allocates less memory than sizeof(te_expr) but treats the returned allocation as a complete te_expr object. This results in undefined behavior and can cause deterministic process termination in UBSan-instrumented builds.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.