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CVE-2026-47703

AdGuard Home: DoQ-to-UDP State Reduction and Source-Port Oracle

6.3 MediumFix available

AdGuard Home is a network-wide software for blocking ads and tracking. Prior to 0.107.75, AdGuard Home's client-triggered DoQ forwarding path to a udp:// upstream reduced backend UDP DNS state by producing dns_id=0 or txid=0 and exposed a quoted-port ICMP source-port oracle, weakening DNS response matching for forwarded queries. This issue is fixed in version 0.107.75.

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
Low
Integrity
Low
Availability
None

Exploit likelihood

0.14%Up 0.1 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.3

AdGuard Home: DoQ-to-UDP State Reduction and Source-Port Oracle

AdGuard Home is a network-wide software for blocking ads and tracking. Prior to 0.107.75, AdGuard Home's client-triggered DoQ forwarding path to a udp:// upstream reduced backend UDP DNS state by producing dns_id=0 or txid=0 and exposed a quoted-port ICMP source-port oracle, weakening DNS response matching for forwarded queries. This issue is fixed in version 0.107.75.

Record
CVE-2026-47703
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Weakness
CWE-330, CWE-346
Updated
2026-11-02
EUVDEUVD-2026-44710 6.3

AdGuard Home is a network-wide software for blocking ads and tracking. Prior to 0.107.75, AdGuard Home's client-triggered DoQ forwarding path to a udp:// upstream reduced backend UDP DNS state by producing dns_id=0 or txid=0 and exposed a quoted-port ICMP source-port oracle, weakening DNS response matching for forwarded queries. This issue is fixed in version 0.107.75.

Record
EUVD-2026-44710
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-xgx4-4h9w-53pv 6.9

AdGuard Home: DoQ-to-UDP State Reduction and Source-Port Oracle

Summary

This report covers the client-triggered DoQ forwarding path in:

  • dnsproxy v0.81.2 (adguard/dnsproxy:v0.81.2)
  • AdGuard Home v0.107.74 (adguard/adguardhome:latest, image version label v0.107.74)

The issue was reproduced on 2026-04-25 with the products configured through their documented DoQ listener and plain UDP upstream surfaces. The scope is the internal backend UDP hop created when a DoQ query is forwarded to a udp:// upstream.

On that path, the backend DNS ID is not preserved as an independent source of entropy. For both products, the backend observer saw dns_id=0 for every sampled client-triggered query on the tested path. Repeated reruns then showed the same txid=0 behavior and the same positive source-port oracle on every sampled run. A separate quoted-port ICMP oracle distinguished the correct backend UDP source port from a wrong one with a stable, client-visible behavior change.

Attached evidence:

Root Cause Analysis

The observable behavior is consistent across both products:

  1. A DoQ client query is accepted on the frontend listener.
  2. The query is forwarded over a backend UDP leg.
  3. On that backend leg, the forwarded DNS ID collapses to 0 on the client-triggered path instead of remaining a fresh per-query variable.
  4. The backend UDP source port is still allocated per query.
  5. When an ICMP error quotes the actual backend source port, the forwarding path flips behavior in a way that does not occur for a wrong quoted port.

That combination removes txid from the backend tuple on the tested path and leaves the UDP source port as the main remaining variable. In practical terms, the backend hop stops behaving like a fresh (txid, source-port) pair per forwarded query and instead becomes a one-variable state exposure.

For dnsproxy, the correct quoted port does more than produce a failure signal: it can push resolution away from the primary UDP upstream and into the fallback upstream. For AdGuard Home, the same condition produces a fast SERVFAIL.

Reproduce

Prerequisites:

  • Docker and Docker Compose
  • OpenSSL
  • build the lab helper image used by the attached harness and observer

The attached reproducer bundle contains only the files needed for this report:

  • scripts: attachments/scripts/
  • helper image build files: attachments/docker/unbound-doq-attacker/
  • compose files: attachments/docker-compose.g03.yml, attachments/docker-compose.g04.yml, attachments/docker-compose.g05.yml
  • shipped evidence: attachments/artifacts/...

Build the helper image first:

  1. cd attachments
  2. docker build -t unbound-doq-attacker:latest -f docker/unbound-doq-attacker/Dockerfile docker/unbound-doq-attacker

To rerun dnsproxy:

  1. cd attachments
  2. bash scripts/repro-g03-dnsproxy-oracle.sh
  3. Inspect artifacts/g03/<RUN_ID>/summary.txt
  4. Inspect artifacts/g03/<RUN_ID>/entropy-backend.jsonl, txid_correct-backend.jsonl, and port_correct-backend.jsonl

To rerun the dnsproxy fallback-steering case:

  1. cd attachments
  2. bash scripts/repro-g04-dnsproxy-steering.sh
  3. Inspect artifacts/g04/<RUN_ID>/summary.txt
  4. Inspect steering_correct-main.jsonl and steering_correct-fallback.jsonl

To rerun AdGuard Home:

  1. cd attachments
  2. bash scripts/repro-g05-adguardhome-oracle.sh
  3. Inspect…
Record
GHSA-xgx4-4h9w-53pv
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-330, CWE-362, CWE-662
Updated
2026-11-02
NVD 6.3

AdGuard Home is a network-wide software for blocking ads and tracking. Prior to 0.107.75, AdGuard Home's client-triggered DoQ forwarding path to a udp:// upstream reduced backend UDP DNS state by producing dns_id=0 or txid=0 and exposed a quoted-port ICMP source-port oracle, weakening DNS response matching for forwarded queries. This issue is fixed in version 0.107.75.

Record
CVE-2026-47703
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness
CWE-330, CWE-346
Updated
2026-11-02
OSV 6.3

AdGuard Home: DoQ-to-UDP State Reduction and Source-Port Oracle

AdGuard Home is a network-wide software for blocking ads and tracking. Prior to 0.107.75, AdGuard Home's client-triggered DoQ forwarding path to a udp:// upstream reduced backend UDP DNS state by producing dns_id=0 or txid=0 and exposed a quoted-port ICMP source-port oracle, weakening DNS response matching for forwarded queries. This issue is fixed in version 0.107.75.

Record
CVE-2026-47703
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Weakness
CWE-330, CWE-346
Updated
2026-11-02
OSVGHSA-xgx4-4h9w-53pv 6.9

AdGuard Home: DoQ-to-UDP State Reduction and Source-Port Oracle

Summary

This report covers the client-triggered DoQ forwarding path in:

  • dnsproxy v0.81.2 (adguard/dnsproxy:v0.81.2)
  • AdGuard Home v0.107.74 (adguard/adguardhome:latest, image version label v0.107.74)

The issue was reproduced on 2026-04-25 with the products configured through their documented DoQ listener and plain UDP upstream surfaces. The scope is the internal backend UDP hop created when a DoQ query is forwarded to a udp:// upstream.

On that path, the backend DNS ID is not preserved as an independent source of entropy. For both products, the backend observer saw dns_id=0 for every sampled client-triggered query on the tested path. Repeated reruns then showed the same txid=0 behavior and the same positive source-port oracle on every sampled run. A separate quoted-port ICMP oracle distinguished the correct backend UDP source port from a wrong one with a stable, client-visible behavior change.

Attached evidence:

Root Cause Analysis

The observable behavior is consistent across both products:

  1. A DoQ client query is accepted on the frontend listener.
  2. The query is forwarded over a backend UDP leg.
  3. On that backend leg, the forwarded DNS ID collapses to 0 on the client-triggered path instead of remaining a fresh per-query variable.
  4. The backend UDP source port is still allocated per query.
  5. When an ICMP error quotes the actual backend source port, the forwarding path flips behavior in a way that does not occur for a wrong quoted port.

That combination removes txid from the backend tuple on the tested path and leaves the UDP source port as the main remaining variable. In practical terms, the backend hop stops behaving like a fresh (txid, source-port) pair per forwarded query and instead becomes a one-variable state exposure.

For dnsproxy, the correct quoted port does more than produce a failure signal: it can push resolution away from the primary UDP upstream and into the fallback upstream. For AdGuard Home, the same condition produces a fast SERVFAIL.

Reproduce

Prerequisites:

  • Docker and Docker Compose
  • OpenSSL
  • build the lab helper image used by the attached harness and observer

The attached reproducer bundle contains only the files needed for this report:

  • scripts: attachments/scripts/
  • helper image build files: attachments/docker/unbound-doq-attacker/
  • compose files: attachments/docker-compose.g03.yml, attachments/docker-compose.g04.yml, attachments/docker-compose.g05.yml
  • shipped evidence: attachments/artifacts/...

Build the helper image first:

  1. cd attachments
  2. docker build -t unbound-doq-attacker:latest -f docker/unbound-doq-attacker/Dockerfile docker/unbound-doq-attacker

To rerun dnsproxy:

  1. cd attachments
  2. bash scripts/repro-g03-dnsproxy-oracle.sh
  3. Inspect artifacts/g03/<RUN_ID>/summary.txt
  4. Inspect artifacts/g03/<RUN_ID>/entropy-backend.jsonl, txid_correct-backend.jsonl, and port_correct-backend.jsonl

To rerun the dnsproxy fallback-steering case:

  1. cd attachments
  2. bash scripts/repro-g04-dnsproxy-steering.sh
  3. Inspect artifacts/g04/<RUN_ID>/summary.txt
  4. Inspect steering_correct-main.jsonl and steering_correct-fallback.jsonl

To rerun AdGuard Home:

  1. cd attachments
  2. bash scripts/repro-g05-adguardhome-oracle.sh
  3. Inspect…
Record
GHSA-xgx4-4h9w-53pv
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-330, CWE-362, CWE-662
Updated
2026-11-02
OSVGO-2026-5756 No score

AdGuard Home: DoQ-to-UDP State Reduction and Source-Port Oracle in github.com/AdguardTeam/AdGuardHome

AdGuard Home: DoQ-to-UDP State Reduction and Source-Port Oracle in github.com/AdguardTeam/AdGuardHome

Record
GO-2026-5756
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/AdguardTeam/AdGuardHome
Go
 through 0.107.74
0.107.75
github.com/AdguardTeam/dnsproxy
Go
 before 0.81.3
0.81.3
github.com/AdguardTeam/AdGuardHome
Go
 before 0.107.75
0.107.75
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

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

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

In short

CVE-2026-47703 is a medium vulnerability (CVSS 6.3) in Adguard Adguardhome, published June 4, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. Fixed in github.com/AdguardTeam/AdGuardHome 0.107.75.

References

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