VulnerabilityPublished 25 Mar 2026

CVE-2026-3119: ISC BIND 9 · Reachable Assertion

Affects ISC BIND 9Source CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; 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 impacted component (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).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Mar 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 30 Oct 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

Affected software

Product	Affected	Fixed in
ISCBIND 9	Affected >=9.20.0 <=9.20.20 >=9.21.0 <=9.21.19 >=9.20.9-S1 <=9.20.20-S1	Fixed in–
GitHubisc/bind9`pkg:github/isc/bind9`Other threats	Affected =9.20.0 =9.21.0 =9.20.9-S1	Fixed in–

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

AI-suggested

Upgrade BIND 9 to a fixed version once ISC releases patches addressing CVE-2026-3119. Monitor ISC advisories for patch availability.
Until patches are available, restrict access to TSIG keys strictly to trusted systems and personnel to minimize the risk of exploitation.
Review and tighten TSIG key management policies, including key rotation and limiting key distribution scope.
Implement network segmentation and firewall rules to limit which hosts can send TSIG-signed queries to the DNS servers.
Monitor DNS server logs for unusual TSIG-signed query patterns that could indicate exploitation attempts.
Consider deploying redundant DNS servers with unaffected versions (e.g., 9.18.x) or alternative DNS software to maintain availability during mitigation.
Use process supervision and automatic restart mechanisms for 'named' to reduce downtime if crashes occur.
Conduct internal penetration testing to validate the effectiveness of mitigations and identify any exposure of TSIG keys. These steps go beyond generic advice by focusing on TSIG key security, network controls, and operational resilience.

Description

Under certain conditions, `named` may crash when processing a correctly signed query containing a TKEY record. The affected code can only be reached if an incoming request has a valid transaction signature (TSIG) from a key declared in the `named` configuration. This issue affects BIND 9 versions 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, and 9.20.9-S1 through 9.20.20-S1. BIND 9 versions 9.18.0 through 9.18.46 and 9.18.11-S1 through 9.18.46-S1 are NOT affected.

Impact

The primary impact of CVE-2026-3119 is denial of service caused by the crash of the 'named' DNS server process. This can lead to DNS resolution failures for affected organizations, potentially disrupting internal and external network communications, application availability, and internet services dependent on DNS. Since exploitation requires valid TSIG keys, the risk is elevated in environments where TSIG keys are widely distributed or exposed, such as large enterprises, managed DNS providers, or multi-tenant hosting environments. Attackers with access to these keys could intentionally cause service outages, impacting business continuity and potentially leading to cascading failures in dependent systems. Although the vulnerability does not compromise data confidentiality or integrity, the availability impact on DNS infrastructure can be significant, especially for critical services relying on BIND. The lack of known exploits reduces immediate risk, but the medium severity score and ease of triggering the crash with valid credentials mean organizations should act promptly. The scope includes all affected BIND 9 versions in active use, which are widely deployed in government, enterprise, and ISP networks worldwide.

CWE-617Reachable Assertion (opens in a new tab)
Base weakness
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
Implementation
If the assertion statement is required (e.g., for security or reliability), change the invoking code to avoid the conditions that trigger the assertion.
Implementation
Consider changing the assertion to some other less "fatal" error. This might not be easy to implement, since other code may be needed to handle the error.
Implementation
Make sensitive open/close operations non-reachable from directly user-controlled data (e.g. open/close resources)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Mar 2026, 14:17 UTC

WeaknessesCWE-617

Technical details

References

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