CVE-2021-42202Public exploit

Denial of service via NULL filter dereference

Published May 31, 2022 · Updated Aug 4, 2024

SWFTools through 20201222 allows local users to cause denial of service via crafted SWF input processed by swfdump. The swf_DeleteFilter function in swffilter.c dereferences a NULL filter pointer while traversing malformed filter data, producing a segmentation fault. Exploitation requires the target to process attacker-controlled SWF content and interrupts the parsing process without evidence of confidentiality or integrity impact.

CVSS severity5.5
Medium
EPSS probability0.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SWFTools through 20201222 allows local users to cause denial of service via crafted SWF input processed by swfdump. The swf_DeleteFilter function in swffilter.c dereferences a NULL filter pointer while traversing malformed filter data, producing a segmentation fault. Exploitation requires the target to process attacker-controlled SWF content and interrupts the parsing process without evidence of confidentiality or integrity impact.

The record

CVE
CVE-2021-42202
Published
May 31, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 31, 2022CVE 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NVDAV: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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1203Exploitation for Client Execution

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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