CVE-2026-8258Public exploit

Local process crash via format-specifier overflow

Published May 11, 2026 · Updated May 11, 2026

Stack buffer overflow in Squirrel 3.0 through 3.2 allows local users to crash the runtime via a crafted string format specifier. validate_format accepts a 20-character specifier because its limit check uses > instead of >=, then memcpy writes 21 bytes into fmt[1] of a 20-byte stack buffer. Exploitation requires local script execution with the string library; the demonstrated result is a runtime abort, while adjacent stack data can be corrupted.

CVSS severity5.3
Medium
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack buffer overflow in Squirrel 3.0 through 3.2 allows local users to crash the runtime via a crafted string format specifier. validate_format accepts a 20-character specifier because its limit check uses > instead of >=, then memcpy writes 21 bytes into fmt[1] of a 20-byte stack buffer. Exploitation requires local script execution with the string library; the demonstrated result is a runtime abort, while adjacent stack data can be corrupted.

The record

CVE
CVE-2026-8258
Published
May 11, 2026
Updated
May 11, 2026
Vendor
Squirrel
Product
Squirrel
Classifications
CWE-119, CWE-121, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 2026CVE publishedPublication date reported by the CVE source.
  2. May 11, 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

4.3VulDB CNAAV:L/AC:L/Au:S/C:P/I:P/A:P
5.3VulDB CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
1.9VulDB CNACVSS: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

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-119Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-121Stack-based Buffer Overflow
T1499Endpoint Denial of Service

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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