CVE-2021-45955Public exploitNetwork attack vector

Heap overwrite via unchecked pseudo-header reinsertion

Published Dec 31, 2021 · Updated Aug 4, 2024

Heap-based buffer overflow in resize_packet in dnsmasq 2.86 allows remote attackers to overwrite heap memory via a crafted packet. Pseudo-header reinsertion lacks a check against the received packet length, so resize_packet can move data beyond allocated packet storage. Reachability requires a packet that triggers resizing; the vendor disputes that this fuzz-discovered condition is a real vulnerability.

CVSS severity9.8
Critical
EPSS probability2.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in resize_packet in dnsmasq 2.86 allows remote attackers to overwrite heap memory via a crafted packet. Pseudo-header reinsertion lacks a check against the received packet length, so resize_packet can move data beyond allocated packet storage. Reachability requires a packet that triggers resizing; the vendor disputes that this fuzz-discovered condition is a real vulnerability.

The record

CVE
CVE-2021-45955
Published
Dec 31, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 31, 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

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write

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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