Quick answer
Direct answer
What is BIND?
ISC BIND is DNS software used to provide name resolution services. Network administrators and infrastructure teams use it wherever applications and users depend on DNS. Its named daemon is the service process at the center of this vulnerability. For your exposure assessment, the important question is not simply whether BIND appears in an inventory, but whether a vulnerable named process is running and reachable.
DNS availability matters because applications need dependable answers when locating services. Think about a business application whose users cannot reach a required service because name resolution is unavailable. The application itself might remain healthy while its users experience an outage. When you assess a DNS vulnerability, map those dependencies instead of treating the affected server as an isolated machine.
This article approaches CVE-2015-5477 through Continuous Threat Exposure Management, or CTEM. Your objective is to connect software evidence, network reachability, business dependencies, and verified remediation. A version finding is the beginning of that process. It does not tell you whether a security update has been incorporated into a vendor package, whether the vulnerable service is active, or what a disruption would mean for your organization.
CVE-2015-5477 at a glance
| Field | Detail |
|---|---|
| CVE ID | CVE-2015-5477 |
| Product | ISC BIND |
| Severity | HIGH |
| CVSS base score | 7.5 |
| CVSS vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| EPSS probability | 99.41 percent (percentile 100) |
| CISA KEV | Yes, added 2026-10-08 |
| Weakness | CWE-19, CWE-617 |
| Affected versions | Junos before 12.1; Junos from 13.1 before 13.2; Junos 12.1; Junos 12.1r; Junos 12.1x44; Junos 12.1x45; Junos 12.1x46; Junos 12.1x47; Junos 12.3; Junos 12.3x48; Junos 12.3x50; Junos 13.2 |
| Published | July 29, 2015 |
CISA required action
What the flaw is
CVE-2015-5477 affects the named daemon in ISC BIND. The supplied description identifies BIND 9.x before 9.9.7-P2 and BIND 9.10.x before 9.10.2-P3. The trigger involves TKEY queries. Processing these queries can cause a REQUIRE assertion failure, followed by daemon exit. The resulting security impact is denial of service: the affected process stops instead of continuing to provide its DNS service.
An assertion checks a condition that the software expects to hold. Here, the important failure is that remotely supplied input can lead to an assertion that terminates the daemon. You do not need to reproduce the triggering query to understand the exposure. The defensive issue is the connection between network input, query processing, and service termination. The supplied weakness identifiers are CWE-19 and CWE-617.
The listed CVSS 7.5 rating is HIGH. Its vector describes a network attack with low complexity, no required privileges, and no user interaction. It assigns the impact to availability, not confidentiality or integrity. Keep that distinction clear: the verified description supports a remotely triggered service outage, not a claim that this flaw directly steals records, changes DNS answers, or executes attacker code.
How an attack could happen
Consider a hypothetical organization with a reachable DNS service running an affected BIND build. The following sequence illustrates the exposure conceptually, without providing a triggering packet or attack procedure. Your actual outcome would depend on the deployed software, access restrictions, and service dependencies.
- 1An attacker can communicate with the affected DNS service. For your assessment, establish which sources can reach that service rather than assuming every installed copy has the same exposure.
- 2The attacker submits a TKEY query that reaches the vulnerable processing path. The verified mechanism is an assertion failure, not credential theft or a user being persuaded to open something.
- 3The REQUIRE assertion fails and named exits. The affected process can no longer answer queries while it is stopped.
- 4Dependent users or applications may experience resolution failures unless another working service handles their needs. Your response should address both service recovery and removal of the vulnerable condition.
Impact
Availability is the central impact. A stopped DNS daemon can interrupt the service it provides, but the scale of the business disruption must be assessed locally. Ask which applications depend on the instance, whether those applications have working alternatives, and whether those alternatives share the same vulnerability. Do not translate one daemon exit into an unsupported claim of a complete organization wide outage.
The supplied record places CVE-2015-5477 in the CISA Known Exploited Vulnerabilities catalog, meaning it is being exploited in the wild. It lists October 8, 2026 as the catalog addition date. Treat that as evidence supporting remediation urgency, not as a date establishing when exploitation first began. The record does not provide an attack timeline, victim list, or campaign attribution.
The supplied EPSS score is 99.41 percent. Use it alongside the known exploitation status and your own exposure evidence, not as a guarantee that a particular server will be attacked. Ransomware association is listed as unknown. Unknown does not mean absent, and it does not justify describing this vulnerability as part of a confirmed ransomware campaign.
Who is affected
Start with the BIND ranges in the vulnerability description: BIND 9.x before 9.9.7-P2 and BIND 9.10.x before 9.10.2-P3. These are the supplied upstream version boundaries. For a packaged deployment, check the vendor advisory and package security status before deciding whether the installed build is vulnerable or remediated. Do not substitute a simple text comparison for vendor specific evidence.
The supplied affected product data also lists Junos before 12.1 and Junos from 13.1 before 13.2. It additionally names Junos 12.1, 12.1r, 12.1x44, 12.1x45, 12.1x46, 12.1x47, 12.3, 12.3x48, 12.3x50, and 13.2. Preserve these entries when checking your inventory rather than compressing them into a broader range that the supplied facts do not establish.
For Junos, consult the referenced Juniper advisory JSA10718 to establish applicability and the appropriate remediation for your release and configuration. The supplied facts do not identify a fixed Junos release. The references also include Fedora and openSUSE security announcements. Use the relevant vendor guidance for package decisions without assuming every release or installation from those vendors is affected.
How to detect it
- Inventory DNS services and identify the process, software build, package source, device platform, and responsible team. Separate confirmed running services from installed software that is not active. Record unknowns explicitly so incomplete discovery does not become an accidental finding of safety.
- Correlate BIND version evidence with the applicable vendor advisory. For Junos assets, compare the recorded release against the supplied affected entries and then check JSA10718. Retain the evidence supporting your conclusion, including any vendor confirmation that a package incorporates the correction.
- Review service and system logs for named exits associated with REQUIRE assertion failures. Such an event is consistent with the described failure mechanism, but an assertion message alone does not prove exploitation of this CVE. Correlate it with software status and available network evidence.
- Look for unexpected DNS service interruptions, repeated process recovery, and related application resolution failures. If query telemetry is available, review TKEY activity around those events. Treat that activity as investigative context, not a standalone signature proving a malicious request.
- Map reachability from the internet and from relevant internal networks through approved exposure checks. Establish which controls actually restrict access to the DNS service. Avoid sending a crash inducing query to production merely to confirm a vulnerability that version and vendor evidence can establish.
How to fix and reduce risk
Do this now
- Assign an owner to every confirmed or suspected affected service. Prioritize reachable deployments with important dependencies, especially internet exposed instances. Track uncertainty as an action item rather than waiting for perfect inventory data before beginning remediation.
- Apply the appropriate vendor security update or mitigation. Use the supplied BIND boundaries to guide assessment, but obtain the correct package or supported upgrade path from the vendor. Check the vendor advisory for fixed Junos releases and other details not established here.
- If an outage or suspected exploitation is under investigation, coordinate recovery with evidence preservation. Capture relevant logs and deployment details where feasible. Restoring the process addresses the immediate interruption, but a restart alone does not establish that the vulnerability has been removed.
If you cannot patch yet
- Where service requirements allow, restrict access to the DNS service to necessary clients and network paths. Validate the restrictions from the relevant source networks. Treat reduced reachability as exposure reduction, not proof that the underlying software flaw is corrected.
- Use only workarounds supported by the applicable vendor guidance. The supplied facts do not establish a configuration switch or packet filtering rule that reliably eliminates this vulnerability. Do not assume that a feature appears unused and therefore its query processing cannot be reached.
Longer term hardening
- Verify the software actually running after remediation, then test normal DNS operation and dependent applications. Record the package evidence, change outcome, remaining exposure, and any exception. Close the finding only when the evidence supports the claimed result.
- The supplied KEV action calls for vendor directed mitigation and applicable CISA BOD 26-04 and Forensics Triage Requirements guidance. It also addresses cloud services and discontinuing use when mitigations are unavailable. Determine which requirements apply to your organization and assess each asset's internet exposure.
The CTEM view
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Define the DNS services and business dependencies that matter to this assessment. Include relevant BIND deployments and Junos assets, but do not assume every device runs an affected service. Set ownership and identify the consequences you need to prevent, such as interruption of a critical application's name resolution. |
| Discover | Combine software inventory with service discovery and vendor advisory review. Your evidence should connect a specific asset to an installed build, a running service, and a reachable network path. Keep uncertain package status visible. Discovery is incomplete when the inventory lists a product name but cannot support an applicability decision. |
| Prioritize | Start with the known exploitation status, CVSS 7.5, and EPSS 99.41 percent, then add local context. Give urgent attention to reachable vulnerable instances supporting important services. Do not let the original publication date, July 29, 2015, turn into a reason to dismiss the finding. Age does not establish remediation. |
| Validate | Validate the exposure and the correction without deliberately causing a production outage. Confirm vendor package status, running software, access controls, and normal service behavior. If you need additional testing, use an approved isolated environment. Distinguish a verified software correction from a temporary restriction that only narrows who can reach the service. |
| Mobilize | Give the responsible team a concrete action package: affected assets, evidence, dependencies, vendor guidance, and acceptance criteria. Coordinate security, network, and service owners around the same result. After deployment, capture proof of remediation and review exceptions so an unresolved DNS exposure does not disappear between teams or maintenance windows. |
Key takeaways
- CVE-2015-5477 is an ISC BIND availability vulnerability in which TKEY query processing can trigger a REQUIRE assertion failure and named exit.
- Known exploitation makes this an operational priority. Use reachability and business dependencies to decide which affected assets need attention first.
- Upstream BIND version boundaries are supplied, but package status and Junos remediation require confirmation through the applicable vendor advisory.
- Assertion failures and service interruptions deserve investigation, but neither a crash nor TKEY activity alone proves exploitation of this CVE.
- A strong CTEM response ends with verified running software, tested service health, documented exposure, and accountable ownership of any remaining exceptions.
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