CVE-2026-9541Public exploit

Application crash via negative bytecode string length

Published May 26, 2026 · Updated May 26, 2026

Heap-based buffer overflow in Squirrel 3.0 through 3.2 allows local users to crash applications by loading crafted .cnut bytecode. ReadObject accepts a negative OT_STRING length, GetScratchPad leaves the existing scratch buffer unchanged, and SafeRead passes the signed value to fread as a large unsigned size. The published proof of concept demonstrates an application crash; arbitrary code execution has not been demonstrated.

CVSS severity5.3
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Squirrel 3.0 through 3.2 allows local users to crash applications by loading crafted .cnut bytecode. ReadObject accepts a negative OT_STRING length, GetScratchPad leaves the existing scratch buffer unchanged, and SafeRead passes the signed value to fread as a large unsigned size. The published proof of concept demonstrates an application crash; arbitrary code execution has not been demonstrated.

The record

CVE
CVE-2026-9541
Published
May 26, 2026
Updated
May 26, 2026
Vendor
Squirrel
Product
Squirrel
Classifications
CWE-122, CWE-119
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 26, 2026CVE publishedPublication date reported by the CVE source.
  2. May 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.0
  2. Affected versionversion=3.1
  3. Affected versionversion=3.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Squirrel · Squirrelversion=3.0; version=3.1; version=3.2

Published CVSS scores

4.3VulDBAV:L/AC:L/Au:S/C:P/I:P/A:P
1.9VulDBCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
5.3VulDBCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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