What is the CVSS score of CVE-2015-5477?

CVE-2015-5477 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 92.8%.

Is there a public PoC exploit available for CVE-2015-5477?

Yes, a public proof-of-concept exploit is available for CVE-2015-5477. Prioritise patching immediately. EPSS: 92.8%.

How to fix or mitigate CVE-2015-5477?

Vendor-released patch: 9.9.7-P2 and 9.10.2-P3. Within 24 hours, inventory all BIND 9.x instances and identify any server running a version before 9.9.7-P2 or 9.10.x before 9.10.2-P3, prioritizing internet-facing DNS resolvers and authoritative servers; apply vendor-released patch upgrades to 9.9.7-P2 or 9.10.2-P3 (or a later supported release) on the highest-exposure systems, and if emergency maintenance is not possible, temporarily restrict DNS query access to trusted networks. Within 7 days, complete patching for all remaining affected BIND instances, verify daemon restarts and DNS service health, and confirm that configuration management and monitoring no longer report vulnerable versions. Within 30 days, perform a full DNS asset reconciliation to find forgotten or shadow BIND deployments, validate that all systems report fixed versions (9.9.7-P2 or 9.10.2-P3 and later), and review logging/alerting for TKEY query anomalies and unexpected BIND process exits.

ISC BIND CVE-2015-5477

HIGH

Data Processing Errors (CWE-19)

2015-07-29 cve@mitre.org

Denial Of Service Bind Isc

7.5

CVSS 3.1 · Vendor: mitre

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Reach exposed BIND named service (UDP/TCP 53)
Exploit

Craft malicious TKEY query
Execution

Send query to trigger REQUIRE assertion
Impact

named daemon exits, DNS offline

Vulnerability Assessment

Weakness	CWE CWE-19 ASVS 5.0 V2 - Validation and Business Logic Data processing
Exploitation Conditions	No special conditions beyond network reachability - a remote unauthenticated attacker can crash default configurations of ISC BIND named simply by sending a crafted TKEY query to the DNS service port (53), per the AV:N/AC:L/PR:N/UI:N vector. TKEY handling is part of standard named processing and does not require a non-default feature to be enabled, so authoritative and recursive servers alike are affected. The practical limiting factor is network exposure: the server must be reachable (directly or via forwarded DNS traffic) by the attacker, and the affected software must be a pre-patch version (before 9.9.7-P2 or 9.10.x before 9.10.2-P3). Impact is limited to denial of service (daemon exit); there is no confidentiality or integrity consequence.
Impact	All signals align toward genuine high priority. The CVSS vector (AV:N/AC:L/PR:N/UI:N) describes a remote, low-complexity, unauthenticated attack with pure availability impact (A:H, C:N/I:N) - consistent with the described assertion-failure denial of service rather than code execution. This is strongly corroborated across sources: EPSS is 92.75% (100th percentile), the flaw is listed in CISA KEV as confirmed actively exploited, and public exploit code exists. There is no conflict between the signals here - the extremely high EPSS, KEV listing, and public POC together indicate widespread, easily automated exploitation, which is credible given that a single crafted TKEY query crashes named. The only nuance is that the high 7.5 score reflects availability impact alone; there is no data exfiltration or RCE risk, so impact is service outage, not compromise. For any internet-facing or recursive BIND resolver this is a confirmed, must-patch issue.
Exploit ScenarioDerived	A remote, unauthenticated attacker sends a specially crafted TKEY DNS query to a vulnerable BIND named server, triggering a REQUIRE assertion failure that causes the daemon to exit and take down DNS service. Public exploit code exists and the flaw is confirmed as actively exploited in CISA KEV, so weaponization is trivial. Repeated queries keep the resolver offline, producing a sustained denial of service across all dependent services.

Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.

Exploited in the wild (CISA KEV) Patch available 92.8% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 08, 2026

Remote unauthenticated attackers can cause a denial-of-service condition in ISC BIND 9.x by sending a crafted TKEY query, leading to an assertion failure and daemon exit (CVE-2015-5477). Affected versions are BIND 9.x before 9.9.7-P2 and 9.10.x before 9.10.2-P3. This vulnerability is confirmed actively exploited (CISA KEV) with publicly available exploit code, and has an EPSS score of 92.75% (100th percentile).

RemediationAI

Upgrade to BIND 9.9.7-P2 or 9.10.2-P3 (or later) to remediate this vulnerability. Specifically, for 9.9.x series upgrade to 9.9.7-P2, and for 9.10.x series upgrade to 9.10.2-P3. Patches are available from vendor and through distribution updates (e.g., Fedora, openSUSE advisories). As a compensating control, restrict network access to the DNS service (TCP/UDP port 53) to trusted clients only; however, this may not be feasible for public-facing DNS servers and could disrupt legitimate traffic. BIND does not provide a configuration option to disable TKEY processing, so patching is the recommended mitigation. Given confirmed active exploitation, immediate patching is critical. Refer to the CISA KEV entry and Juniper advisory for additional details.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The vulnerability resides in ISC BIND's handling of TKEY queries, a DNS resource record type defined in RFC 2930 for establishing transaction keys used in TSIG. A crafted TKEY query triggers a REQUIRE assertion failure in the named daemon, causing it to exit. This is classified as CWE-19 (Data Processing Errors), indicating a failure to properly validate or process input data. The affected component is the named DNS server, and the flaw is reachable in default configurations because TKEY processing is part of standard DNS query handling. The CPE strings cpe:2.3:a:isc:bind:*:p1:*:*:*:*:*:* and cpe:2.3:a:isc:bind:*:p2:*:*:*:*:*:* indicate specific patch levels, but the vulnerable versions are all releases prior to 9.9.7-P2 and 9.10.2-P3.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (mitre) PRIMARY 7.5 HIGH

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

vuln.today AI 7.5 HIGH

A single crafted TKEY query from an unauthenticated remote attacker reliably crashes named (AV:N/AC:L/PR:N/UI:N), causing availability loss only (A:H, C:N/I:N).

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

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

Primary rating from Vendor (mitre).

CVSS VectorVendor: mitre

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Updated

Oct 08, 2026 - 18:27 vuln.today

v1 - CVSS changed

CVSS changed

Oct 08, 2026 - 18:23 NVD

7.8 (HIGH) 7.5 (HIGH)

Added to CISA KEV

Oct 08, 2026 - 18:03 CISA

CVE Published

Jul 29, 2015 - 14:59 cve.org

HIGH 7.8

DescriptionCVE.org

named in ISC BIND 9.x before 9.9.7-P2 and 9.10.x before 9.10.2-P3 allows remote attackers to cause a denial of service (REQUIRE assertion failure and daemon exit) via TKEY queries.

Executive ViewAI

Why It Matters

ISC BIND, a foundational DNS service used across many organizations, is affected by a high-severity denial-of-service flaw that can abruptly stop DNS resolution on vulnerable servers. This issue is confirmed actively exploited (CISA KEV) and publicly available exploit code exists, creating an immediate availability risk for internet-facing and internal name resolution that can cascade into email, authentication, and application outages. Leadership should prioritize urgent patching because loss of DNS can quickly disrupt business-critical services and customer-facing operations.

Business Impact: High

Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

Threat Score

9.3/10

Composite threat intelligence

EPSS Score

92.8%

Top 0% exploitable

Prevalence

Ubiquitous

ISC BIND is the most widely deployed DNS server software globally

Threat Intel

1 sources

Exploit

POC

Public exploit code exists

Data Quality

7 sources

Confidence: High

NVD

CVE.org

CISA KEV

EPSS CISA POC (1)

Exploit-DB

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV Yes

Public POC Yes

EPSS 92.8%

Patch available Yes

Active threat Yes

Deciding rule

In CISA KEV with patch available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Immediate

Exploitation· derived

Active

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

High

Priority Score

211

Low Medium High Critical

KEV: +50

EPSS: +93

CVSS: +38

PoC: +20

Weaponized: 0

Threat intel: +10

Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)CVE.org

cpe:2.3:a:isc:bind:*:p1:*:*:*:*:*:*

cpe:2.3:a:isc:bind:*:p2:*:*:*:*:*:*

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CVE-2016-9147 HIGH Act Now

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CVE-2016-2848 HIGH Act Now

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Same weakness CWE-19 – Data Processing Errors

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CVE-2012-5357 CRITICAL POC

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CVE-2016-4977 HIGH POC

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CVE-2015-5374 HIGH POC

7.8

CVE-2016-3236 CRITICAL POC

9.8

CVE-2015-0097 CRITICAL POC

9.3

CVE-2015-0081 CRITICAL POC

9.3

CVE-2014-8598 MEDIUM POC

6.4

CVE-2015-2373 CRITICAL

10.0

Same technique Denial Of Service

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CVE-2011-2462 CRITICAL POC

9.8

CVE-2011-0611 HIGH POC

8.8

CVE-2012-1889 HIGH POC

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CVE-2012-0507 CRITICAL POC

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CVE-2014-1761 HIGH POC

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CVE-2015-5122 CRITICAL POC

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CVE-2011-0609 HIGH POC

7.8

Threat IntelligenceMISP

CISA Advisories

AA26-281A

Sources: Metasploit/Nuclei, CISA (public domain)

References

Advisories & patches

PATCH https://kb.isc.org/article/AA-01272 ADVISORY https://vuldb.com/vuln/76834 REF http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10718 REF http://lists.fedoraproject.org/pipermail/package-announce/2015-August/163006.html REF http://lists.fedoraproject.org/pipermail/package-announce/2015-August/163007.html REF http://lists.fedoraproject.org/pipermail/package-announce/2015-August/163015.html REF http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00043.html REF http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00044.html REF http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00045.html REF http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00048.html REF http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00050.html REF http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00001.html REF http://lists.opensuse.org/opensuse-security-announce/2016-01/msg00033.html REF http://marc.info/?l=bugtraq&m=144000632319155&w=2 REF http://marc.info/?l=bugtraq&m=144017354030745&w=2 REF http://marc.info/?l=bugtraq&m=144181171013996&w=2 REF http://marc.info/?l=bugtraq&m=144294073801304&w=2 REF http://packetstormsecurity.com/files/132926/BIND-TKEY-Query-Denial-Of-Service.html REF http://rhn.redhat.com/errata/RHSA-2015-1513.html REF http://rhn.redhat.com/errata/RHSA-2015-1514.html REF http://rhn.redhat.com/errata/RHSA-2015-1515.html REF http://rhn.redhat.com/errata/RHSA-2016-0078.html REF http://rhn.redhat.com/errata/RHSA-2016-0079.html REF http://www.debian.org/security/2015/dsa-3319 REF http://www.oracle.com/technetwork/topics/security/bulletinjul2015-2511963.html REF http://www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html REF http://www.securityfocus.com/bid/76092 REF http://www.securitytracker.com/id/1033100 REF http://www.ubuntu.com/usn/USN-2693-1 REF https://h20564.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c04789415 REF https://h20564.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c04952480 REF https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05095918 REF https://kb.isc.org/article/AA-01305 REF https://kb.isc.org/article/AA-01306 REF https://kb.isc.org/article/AA-01307 REF https://kb.isc.org/article/AA-01438 REF https://kb.juniper.net/JSA10783 REF https://kc.mcafee.com/corporate/index?page=content&id=SB10126 REF https://security.gentoo.org/glsa/201510-01 REF https://security.netapp.com/advisory/ntap-20160114-0001/ REF https://support.apple.com/kb/HT205032 REF https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2015-5477

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