CVE-2026-33596

Query-response mismatch via TCP stream ID overflow

Published Apr 22, 2026 · Updated Apr 22, 2026

Integer overflow in PowerDNS DNSdist 1.9.0 through 1.9.12 and 2.0.0 through 2.0.3 allows remote attackers to mismatch DNS responses. The outgoing DNS-over-TCP path in dnsdist-tcp-downstream.hh lets its stream identifier overflow, allowing backend replies to be associated with different queued queries. Exploitation requires a flood of perfectly timed queries routed to a TCP-only or DNS-over-TLS backend; no system compromise is reported.

CVSS severity3.1
Low
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in PowerDNS DNSdist 1.9.0 through 1.9.12 and 2.0.0 through 2.0.3 allows remote attackers to mismatch DNS responses. The outgoing DNS-over-TCP path in dnsdist-tcp-downstream.hh lets its stream identifier overflow, allowing backend replies to be associated with different queued queries. Exploitation requires a flood of perfectly timed queries routed to a TCP-only or DNS-over-TLS backend; no system compromise is reported.

The record

CVE
CVE-2026-33596
Published
Apr 22, 2026
Updated
Apr 22, 2026
Vendor
PowerDNS
Product
DNSdist
Classifications
CWE-190, T1499
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.9.0 <1.9.13
  2. Affected versionversion=2.0.0 <2.0.4

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

PowerDNS · DNSdistversion=1.9.0 <1.9.13; version=2.0.0 <2.0.4

Published CVSS scores

6.5NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1Open-XchangeCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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