CVE-2021-33833Network attack vector

Remote code execution via unchecked DNS reply copy

Published Jun 9, 2021 · Updated Aug 3, 2024

Stack-based buffer overflow in ConnMan 1.30 through 1.39 allows remote attackers to execute code through crafted DNS replies. The dnsproxy.c uncompress function copies A or AAAA record NAME and RDATA data into a stack buffer without adequately checking RDLENGTH. Exploitation requires a malicious DNS server response; the reported PoC required PIE and stack-overflow protections to be disabled.

CVSS severity9.8
Critical
EPSS probability2.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in ConnMan 1.30 through 1.39 allows remote attackers to execute code through crafted DNS replies. The dnsproxy.c uncompress function copies A or AAAA record NAME and RDATA data into a stack buffer without adequately checking RDLENGTH. Exploitation requires a malicious DNS server response; the reported PoC required PIE and stack-overflow protections to be disabled.

The record

CVE
CVE-2021-33833
Published
Jun 9, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1203
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Jun 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

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

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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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