VulnerabilityPublished 8 Nov 2026

CVE-2026-123570: hickory-dns · Uncontrolled Resource Consumption

Affects hickory-dnsSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 0.26.2 soon.

Data as of 8 Nov 2026, 02:05 UTC

CVSS 4.0 base score

8.7High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (VulnCheck)	CVSS 4.0	8.7
CNA (VulnCheck)	CVSS 3.1	7.5

Patch: Available – fixed in 0.26.2

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: High
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade hickory-dns to 0.26.2.

Affected software

Product	Affected	Fixed in
hickory-dnshickory-dns	Affected >=0.18 <0.26.2	Fixed in 0.26.2
crates.iohickory-dns`pkg:cargo/hickory-dns`Other threats	Affected >=0.18 <0.26.2	Fixed in 0.26.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade hickory-dns to version 0.26.2 or later, where this vulnerability is fixed. No other mitigation or temporary workaround is indicated.

Description

CVE-2026-123570 is a high-severity vulnerability in hickory-dns versions 0.18 up to but not including 0.26.2. The DNS wire-format message parser preallocates memory based on untrusted header fields (ANCOUNT, NSCOUNT, ARCOUNT), which can be manipulated by remote attackers to cause excessive memory allocation of about 18MB per message. This can lead to uncontrolled resource consumption and potential denial of service.

Impact

Remote attackers can exploit this vulnerability by sending specially crafted UDP datagrams or spoofed responses with large count values in the DNS header fields, causing the vulnerable software to allocate excessive memory. This can result in denial of service due to resource exhaustion. There is no indication of privilege escalation or code execution from the provided data.

Summary

The vulnerability exists in the DNS wire-format message parser of hickory-proto (Hickory DNS) versions >=0.18 and <0.26.2. The parser uses the untrusted ANCOUNT, NSCOUNT, and ARCOUNT header fields to preallocate record vectors before reading the actual record data. An attacker can send a UDP datagram or spoof a response with these counts set to 65535, forcing the parser to allocate approximately 18MB of memory per message, leading to uncontrolled resource consumption. This flaw was fixed in version 0.26.2.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 8 Nov 2026, 02:05 UTC

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