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CVE-2026-42004

EDNS options smuggling

3.7 LowFix available

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
None

Exploit likelihood

0.22%Up 0.1 points since Jun 26, 2026
90%50%10%1%

What each source reports

CVE List Score used 3.7

EDNS options smuggling

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Record
CVE-2026-42004
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness
CWE-115
Updated
2026-11-02
EUVDEUVD-2026-39351 3.7

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Record
EUVD-2026-39351
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-q4qq-c3qm-82jj 3.7

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules,...

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Record
GHSA-q4qq-c3qm-82jj
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness
CWE-115
Updated
2026-11-02
NVD 3.7

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Record
CVE-2026-42004
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness
CWE-115
Updated
2026-11-02
OSV 3.7

EDNS options smuggling

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Record
CVE-2026-42004
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2026-42004 3.7

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Record
DEBIAN-CVE-2026-42004
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Updated
2026-11-02
Show 5 moreShow less
OSVUBUNTU-CVE-2026-42004 3.7

An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.

Record
UBUNTU-CVE-2026-42004
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Updated
2026-11-02
OSVopenSUSE-SU-2026:11411-1 No score

dnsdist-2.0.7-1.1 on GA media

These are all security issues fixed in the dnsdist-2.0.7-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11411-1
Updated
2026-11-02
OSVopenSUSE-SU-2026:21533-1 No score

Security update for dnsdist

This update for dnsdist fixes the following issues:

Update to 1.9.15.

Changes for dnsdist:

Security issues fixed:

  • CVE-2026-40011: invalid output produced in the prometheus endpoint when a large number of crafted DNS queries are sent (bsc#1269204).
  • CVE-2026-40208: processing of DoH3 queries can be delayed via DoH3 GET queries with an invalid DATA frames (bsc#1269207).
  • CVE-2026-40209: outgoing TCP connections to backend can get stuck until a timeout occurs when specially crafted IXFR queries are sent (bsc#1269206).
  • CVE-2026-40210: out-of-bounds read when SetMacAddrAction is used can lead to uninitialized memory being sent over the network or a crash (bsc#1269205).
  • CVE-2026-40211: crafted DNS over HTTP/3 queries can trigger an exception that prevents memory from being freed and can lead to an OOM condition (bsc#1269203).
  • CVE-2026-42004: crafted EDNS OPT record will be ignored by filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted (bsc#1269202).
  • CVE-2026-42005: crafted web request can cause unlimited memory allocation in the internal web server and lead to a DoS (bsc#1269201).
Record
openSUSE-SU-2026:21533-1
Updated
2026-11-02
OSVSUSE-SU-2026:23123-1 No score

Security update for dnsdist

This update for dnsdist fixes the following issues:

Update to 1.9.15.

Changes for dnsdist:

Security issues fixed:

  • CVE-2026-40011: invalid output produced in the prometheus endpoint when a large number of crafted DNS queries are sent (bsc#1269204).
  • CVE-2026-40208: processing of DoH3 queries can be delayed via DoH3 GET queries with an invalid DATA frames (bsc#1269207).
  • CVE-2026-40209: outgoing TCP connections to backend can get stuck until a timeout occurs when specially crafted IXFR queries are sent (bsc#1269206).
  • CVE-2026-40210: out-of-bounds read when SetMacAddrAction is used can lead to uninitialized memory being sent over the network or a crash (bsc#1269205).
  • CVE-2026-40211: crafted DNS over HTTP/3 queries can trigger an exception that prevents memory from being freed and can lead to an OOM condition (bsc#1269203).
  • CVE-2026-42004: crafted EDNS OPT record will be ignored by filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted (bsc#1269202).
  • CVE-2026-42005: crafted web request can cause unlimited memory allocation in the internal web server and lead to a DoS (bsc#1269201).
Record
SUSE-SU-2026:23123-1
Updated
2026-11-02
OSVSUSE-SU-2026:23146-1 No score

Security update for dnsdist

This update for dnsdist fixes the following issues:

Update to 1.9.15.

Changes for dnsdist:

Security issues fixed:

  • CVE-2026-40011: invalid output produced in the prometheus endpoint when a large number of crafted DNS queries are sent (bsc#1269204).
  • CVE-2026-40208: processing of DoH3 queries can be delayed via DoH3 GET queries with an invalid DATA frames (bsc#1269207).
  • CVE-2026-40209: outgoing TCP connections to backend can get stuck until a timeout occurs when specially crafted IXFR queries are sent (bsc#1269206).
  • CVE-2026-40210: out-of-bounds read when SetMacAddrAction is used can lead to uninitialized memory being sent over the network or a crash (bsc#1269205).
  • CVE-2026-40211: crafted DNS over HTTP/3 queries can trigger an exception that prevents memory from being freed and can lead to an OOM condition (bsc#1269203).
  • CVE-2026-42004: crafted EDNS OPT record will be ignored by filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted (bsc#1269202).
  • CVE-2026-42005: crafted web request can cause unlimited memory allocation in the internal web server and lead to a DoS (bsc#1269201).
Record
SUSE-SU-2026:23146-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
dnsdist
Debian:12
 All versions, plus listed versions
1.7.3-21.8.0-11.8.1-11.8.2-11.8.2-2
Show 33 moreShow less
1.8.2-31.8.3-11.8.3-21.8.3-31.9.10-11.9.3-11.9.4-11.9.5-11.9.6-11.9.8-11.9.9-12.0.0-12.0.0-22.0.0-32.0.0-42.0.0-52.0.0-62.0.0~rc1-12.0.0~rc1-22.0.0~rc2-12.0.1-12.0.2-12.0.3-12.0.4-12.0.5-12.0.5-22.0.5-32.0.6-12.1.0-12.1.0-22.1.1-12.1.2-12.1.3-1
 None known
dnsdist
Debian:13
 before 1.9.15-0+deb13u1, plus listed versions
1.9.10-11.9.10-1+deb13u11.9.14-0+deb13u1
1.9.15-0+deb13u1
dnsdist
Debian:14
 before 2.1.0-1, plus listed versions
1.9.10-12.0.0-12.0.0-22.0.0-32.0.0-4
Show 13 moreShow less
2.0.0-52.0.0-62.0.0~rc1-12.0.0~rc1-22.0.0~rc2-12.0.1-12.0.2-12.0.3-12.0.4-12.0.5-12.0.5-22.0.5-32.0.6-1
2.1.0-1
dnsdist
SUSE:Linux Enterprise Server 16.0
From an advisory covering 7 CVEs
 before 1.9.15-160000.1.1
1.9.15-160000.1.1
dnsdist
SUSE:Linux Enterprise Server for SAP applications 16.0
From an advisory covering 7 CVEs
 before 1.9.15-160000.1.1
1.9.15-160000.1.1
dnsdist
Ubuntu:16.04:LTS
 All versions, plus listed versions
1.0.0~alpha2-1
 None known
dnsdist
Ubuntu:Pro:18.04:LTS
 All versions, plus listed versions
1.2.0-11.2.0-31.2.1-11.2.1-1build11.2.1-1ubuntu0.1~esm1
 None known
dnsdist
Ubuntu:Pro:20.04:LTS
 All versions, plus listed versions
1.4.0~rc3-11.4.0-11.4.0-1build11.4.0-1build21.4.0-1ubuntu0.1~esm1
 None known
dnsdist
Ubuntu:Pro:22.04:LTS
 All versions, plus listed versions
1.5.1-3build21.6.1-1build11.6.1-1ubuntu0.1~esm11.6.1-1ubuntu0.1~esm2
 None known
dnsdist
Ubuntu:Pro:24.04:LTS
 All versions, plus listed versions
1.8.0-11.8.2-11.8.2-21.8.2-31.8.3-1
Show 4 moreShow less
1.8.3-21.8.3-2build11.8.3-2build21.8.3-2ubuntu0.1~esm1
 None known
Show 5 moreShow less
Affected packages
PackageAffectedFixed
dnsdist
Ubuntu:25.10
 All versions, plus listed versions
1.9.8-11.9.10-11.9.10-1ubuntu0.1
 None known
dnsdist
Ubuntu:26.10
 All versions, plus listed versions
2.0.2-1build12.0.5-2ubuntu12.0.5-2ubuntu3
 None known
dnsdist
Ubuntu:26.04:LTS
 All versions, plus listed versions
1.9.10-12.0.1-12.0.2-12.0.2-1build1
 None known
dnsdist
openSUSE:Tumbleweed
From an advisory covering 7 CVEs
 before 2.0.7-1.1
2.0.7-1.1
dnsdist
openSUSE:Leap 16.0
From an advisory covering 7 CVEs
 before 1.9.15-160000.1.1
1.9.15-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-42004 is a low vulnerability (CVSS 3.7) in Powerdns Dnsdist, published June 25, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 13th percentile. Fixed in dnsdist 1.9.15-0+deb13u1.

References

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