CVE-2021-39923Public exploitNetwork attack vector

Service interruption via excessive PNRP dissection loop

Published Nov 19, 2021 · Updated Aug 4, 2024

Excessive iteration in Wireshark 3.2.0 through 3.2.17 and 3.4.0 through 3.4.9 allows remote attackers to interrupt service. The PNRP dissector repeatedly adds the pnrp.segment.authority.flags.Lbit field to the protocol tree, exceeding one million items. A malformed packet reaching an active capture needs no authentication or user interaction; opening a crafted trace provides a second path to sustained CPU consumption.

CVSS severity7.5
High
EPSS probability1.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Excessive iteration in Wireshark 3.2.0 through 3.2.17 and 3.4.0 through 3.4.9 allows remote attackers to interrupt service. The PNRP dissector repeatedly adds the pnrp.segment.authority.flags.Lbit field to the protocol tree, exceeding one million items. A malformed packet reaching an active capture needs no authentication or user interaction; opening a crafted trace provides a second path to sustained CPU consumption.

The record

CVE
CVE-2021-39923
Published
Nov 19, 2021
Updated
Aug 4, 2024
Vendor
Wireshark Foundation
Product
Wireshark
Classifications
CWE-834, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 19, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>=3.2.0, <3.2.18
  2. Affected versionversion=>=3.4.0, <3.4.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Wireshark Foundation · Wiresharkversion=>=3.2.0, <3.2.18; version=>=3.4.0, <3.4.10

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5GitLab Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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

Weakness, pattern, technique

CWE-834Excessive Iteration
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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