CVE-2026-2240Public exploit

Local compiler crash via upvalue bitmap overread

Published Feb 9, 2026 · Updated Feb 9, 2026

Out-of-bounds read in Janet 1.40.0 and 1.40.1 allows local users to crash the compiler by compiling crafted source code. janetc_pop_funcdef allocates a closure bitmap from slotchunks but tests the larger upvalue count before reading chunks[7], so a small allocation is indexed out of bounds. The public reproducer invokes the compiler locally and demonstrates an AddressSanitizer abort; no remote path or disclosure of the read bytes is reported.

CVSS severity6.1
Medium
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Janet 1.40.0 and 1.40.1 allows local users to crash the compiler by compiling crafted source code. janetc_pop_funcdef allocates a closure bitmap from slotchunks but tests the larger upvalue count before reading chunks[7], so a small allocation is indexed out of bounds. The public reproducer invokes the compiler locally and demonstrates an AddressSanitizer abort; no remote path or disclosure of the read bytes is reported.

The record

CVE
CVE-2026-2240
Published
Feb 9, 2026
Updated
Feb 9, 2026
Vendor
Janet Language
Product
Janet
Classifications
CWE-125, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 9, 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=1.40.0
  2. Affected versionversion=1.40.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Janet Language · Janetversion=1.40.0; version=1.40.1

Published CVSS scores

3.3VulDBCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
6.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H
1.9VulDBCVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
1.7VulDBAV:L/AC:L/Au:S/C:N/I:N/A: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499.004Application or System Exploitation

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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