CVE-2025-5621VulnerabilityPublished 4 Jun 2025

CVE-2025-5621: D-Link DIR-816 · OS Command Injection

Affects D-Link DIR-816Source CVE Database V5

Not known to be exploited · CVSS 6.9 Medium · end of life, no fix coming : replace or isolate D-Link DIR-816; no fix will be released.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 4.0 base score

6.9Medium

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

EPSS: 7.4% chance of exploitation in 30 days – higher than 94% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: None coming – the product is end of life

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: Low
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
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 4 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 2026-10-25.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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

No fix will be released: D-Link DIR-816 is end of life. Replace it, or isolate it from untrusted networks until you can.

AI-suggested

Since the affected D-Link DIR-816 devices are no longer supported and no official patches are available, European organizations should prioritize the following mitigations: 1) Immediate inventory and identification of all DIR-816 routers running firmware version 1.10CNB05 or similar affected versions. 2) Replace or upgrade affected devices with currently supported hardware that receives regular security updates. 3) If replacement is not immediately feasible, isolate the vulnerable routers from direct internet exposure by placing them behind firewalls or network segmentation controls to restrict access to the /goform/qosClassifier endpoint. 4) Employ network intrusion detection/prevention systems (IDS/IPS) to monitor and block suspicious traffic patterns indicative of command injection attempts targeting these devices. 5) Disable or restrict QoS features if possible, to reduce the attack surface related to the vulnerable function. 6) Implement strict network access controls and ensure that management interfaces are not accessible from untrusted networks. 7) Educate IT staff and users about the risks associated with unsupported network devices and the importance of timely hardware lifecycle management.

Description

A vulnerability has been found in D-Link DIR-816 1.10CNB05 and classified as critical. Affected by this vulnerability is the function qosClassifier of the file /goform/qosClassifier. The manipulation of the argument dip_address/sip_address leads to os command injection. The attack can be launched remotely. The exploit has been disclosed to the public and may be used. This vulnerability only affects products that are no longer supported by the maintainer.

Impact

For European organizations, this vulnerability poses a significant risk, especially for those using the affected D-Link DIR-816 routers in their network infrastructure. Compromise of these routers could lead to unauthorized access to internal networks, interception or manipulation of network traffic, and disruption of critical network services. Given that the device is a consumer-grade router, it may be deployed in small offices or home office environments, which are often less monitored and secured, making them attractive targets for attackers seeking entry points into larger corporate networks. The lack of vendor support means organizations cannot rely on official patches, increasing the likelihood that vulnerable devices remain in operation. This could facilitate lateral movement by attackers within European networks, data exfiltration, or launching further attacks on connected systems. The vulnerability's remote exploitability without authentication further exacerbates the risk, as attackers can scan for and target exposed devices directly over the internet or internal networks.

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 7 Jul 2025, 04:10 UTC

Technical details

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