CVE-2021-39532Public exploitNetwork attack vector

Application crash via slaxLexer null pointer dereference

Published Sep 20, 2021 · Updated Aug 4, 2024

NULL pointer dereference in libslax 0.22.1 and earlier allows remote attackers to crash slaxproc through a crafted SLAX file. The CVE record identifies slaxLexer in slaxlexer.c but does not disclose the parser state or value that becomes null; its linked upstream issue instead demonstrates an out-of-bounds read in the same function. Exploitation requires an application or user to pass attacker-controlled SLAX input to the parser, and the documented consequence is process termination rather than code execution or data access.

CVSS severity6.5
Medium
EPSS probability0.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in libslax 0.22.1 and earlier allows remote attackers to crash slaxproc through a crafted SLAX file. The CVE record identifies slaxLexer in slaxlexer.c but does not disclose the parser state or value that becomes null; its linked upstream issue instead demonstrates an out-of-bounds read in the same function. Exploitation requires an application or user to pass attacker-controlled SLAX input to the parser, and the documented consequence is process termination rather than code execution or data access.

The record

CVE
CVE-2021-39532
Published
Sep 20, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/Au:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
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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