CVE-2019-25042Public exploit

Memory corruption via pre-check compressed-name copy

Published Apr 27, 2021 · Updated Aug 5, 2024

Out-of-bounds write in rdata_copy in NLnet Labs Unbound before 1.9.5 allows attackers to corrupt memory via a compressed DNS name. The function calls memmove before its log_assert check when len exceeds pkt_len, so copying occurs before the oversized length is rejected. Upstream disputes the vulnerability because earlier packet-parsing checks prevent remote or local inputs from reaching this state in a running installation.

CVSS severity9.8
Critical
EPSS probability2.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in rdata_copy in NLnet Labs Unbound before 1.9.5 allows attackers to corrupt memory via a compressed DNS name. The function calls memmove before its log_assert check when len exceeds pkt_len, so copying occurs before the oversized length is rejected. Upstream disputes the vulnerability because earlier packet-parsing checks prevent remote or local inputs from reaching this state in a running installation.

The record

CVE
CVE-2019-25042
Published
Apr 27, 2021
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Apr 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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 vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5SUSECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
9.8Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS: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)
VectorUnavailable
PrivilegesUnavailable
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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