CVE-2020-29557
D-Link DIR-825 R1 Devices Buffer Overflow Vulnerability
Description
CVE-2020-29557 is a CRITICAL buffer overflow vulnerability affecting D-Link DIR-825 R1 devices, carrying a CVSS 3.1 score of 9.8. A buffer overflow in the web interface of D-Link DIR-825 R1 devices through firmware version 3.0.1 allows remote attackers to achieve pre-authentication remote code execution. This CVE is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog with a remediation deadline of 2022-05-03. With an EPSS score of 0.89773 (99.57th percentile), this vulnerability demonstrates extremely high real-world exploitation activity and requires immediate remediation.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| dlink | dir-825 r1 firmware | <= 3.0.1 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://shaqed.github.io/dlink/(Broken Link, Exploit, Third Party Advisory)
- https://www.dlink.ru/ru/download2/5/19/2354/441/(Product)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-29557(US Government Resource)
Weakness Type
CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVE-2020-29557 is classified under CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer. This weakness occurs when software performs operations on a memory buffer without properly restricting the size of data written to or read from that buffer. When more data is written than the buffer can hold, adjacent memory is overwritten, which can corrupt program data, alter control flow, crash the application, or enable arbitrary code execution.
In the context of D-Link DIR-825 R1 devices, this buffer overflow in the web interface is particularly dangerous because it enables pre-authentication remote code execution. Embedded networking devices like consumer routers typically run with elevated privileges and lack security mitigations common in modern operating systems (such as ASLR, stack canaries, or DEP), making buffer overflows trivially exploitable. Once code execution is achieved on a router, attackers gain complete control over the device and all network traffic passing through it.
Learn more: CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer
Impact Analysis
CVE-2020-29557 carries a CVSS 3.1 score of 9.8 (CRITICAL) with Unchanged Scope.
Confidentiality (HIGH): Successful exploitation grants the attacker full access to all data on the router, including network configuration, WiFi credentials, connected device information, DNS settings, VPN configurations, and potentially intercepted network traffic from all connected devices.
Integrity (HIGH): Attackers can completely modify the router's configuration, firmware, DNS settings, and routing tables. This enables man-in-the-middle attacks, traffic redirection to malicious servers, firmware replacement with backdoored versions, and manipulation of all network traffic.
Availability (HIGH): Complete disruption of network services is possible, including bricking the device through destructive firmware modifications, denial of service for all connected devices, and rendering the router permanently inoperable.
Scope Unchanged: The vulnerability's scope is technically Unchanged within the CVSS framework, but the practical impact extends to all devices and users relying on the compromised router for network connectivity.
With an EPSS score of 0.89773 (99.57th percentile), this vulnerability ranks among the most likely to be exploited globally.
Exploit Maturity
CVE-2020-29557 has confirmed active exploitation in the wild and is listed in CISA's Known Exploited Vulnerabilities catalog.
Exploit status: This vulnerability is actively exploited as confirmed by its KEV listing. The EPSS score of 0.89773 (99.57th percentile) places it among the most exploited vulnerabilities tracked. The pre-authentication nature of the vulnerability and the simplicity of buffer overflow exploitation on embedded devices lower the barrier to attack significantly.
Ransomware association: No direct ransomware association has been confirmed for CVE-2020-29557 per current KEV data. However, compromised routers are commonly recruited into botnets (such as Mirai variants) for DDoS attacks, cryptomining, and as proxy infrastructure for other criminal activities.
Attack surface: D-Link DIR-825 R1 routers with web interfaces accessible from the internet (or from the local network) are vulnerable. The vulnerability requires no authentication, making any reachable device an immediate target. IoT search engines commonly index these devices, enabling automated mass exploitation.
KEV deadline: CISA required federal agencies to remediate this vulnerability by 2022-05-03. All organizations and consumers using affected devices should update or replace them immediately.
Remediation
- Apply firmware updates immediately. Update the D-Link DIR-825 R1 to a firmware version released after November 20, 2020, which addresses this vulnerability. Check the D-Link support website for the latest available firmware.
- If no firmware update is available, replace the device. If D-Link has discontinued support for your specific hardware revision and no patch is available, replace the router with a currently supported model. End-of-life networking devices should not remain in production.
- Disable remote management access. Ensure that the router's web management interface is not accessible from the internet. Disable WAN-side management access in the router configuration to reduce the attack surface.
- Implement network segmentation. If the device cannot be immediately replaced or patched, place it behind a firewall and restrict access to its management interface to trusted hosts only.
- Scan for signs of compromise. Check the router for unexpected configuration changes, unfamiliar DNS settings, unknown connected devices, or firmware modifications that could indicate exploitation.
- Monitor for botnet activity. Watch for unusual outbound traffic from the router's network, which could indicate enrollment in a botnet. Deploy network monitoring to detect anomalous traffic patterns.
Technical Details
CVE-2020-29557 is a CRITICAL-severity buffer overflow vulnerability in D-Link DIR-825 R1 devices exploitable remotely over the network without authentication. The attack complexity is low, requiring no specialized conditions. No privileges or user interaction are needed.
Technical mechanism: The vulnerability exists in the web interface of D-Link DIR-825 R1 devices running firmware through version 3.0.1. The web server component fails to properly validate the length of user-supplied input before copying it into a fixed-size buffer in memory. By sending a specially crafted HTTP request with oversized input, an attacker can overflow the buffer and overwrite adjacent memory, including return addresses or function pointers. This allows the attacker to redirect program execution to attacker-controlled code, achieving pre-authentication remote code execution with the privileges of the web server process (typically root on embedded devices).
Affected products and versions: D-Link DIR-825 R1 firmware versions up to and including 3.0.1.
CVSS 3.1 vector analysis: The vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H reflects a network-accessible, low-complexity attack requiring no privileges or user interaction, with maximum impact across confidentiality, integrity, and availability.
Frequently Asked Questions
Is CVE-2020-29557 being actively exploited?
Yes, CVE-2020-29557 is actively exploited in the wild. It is listed in CISA's Known Exploited Vulnerabilities catalog, and its EPSS score of 0.89773 (99.57th percentile) confirms extremely high exploitation probability. The pre-authentication nature makes exploitation straightforward for attackers.
What products are affected by CVE-2020-29557?
CVE-2020-29557 affects D-Link DIR-825 R1 devices running firmware versions up to and including 3.0.1. Check your device's firmware version through the web administration interface. D-Link released a firmware update after November 20, 2020 to address this issue.
How do I fix CVE-2020-29557?
Update the D-Link DIR-825 R1 firmware to the latest version available from D-Link's support website. If the device is end-of-life and no patch is available, replace it with a currently supported router. As an interim measure, disable remote management access and restrict management interface access to trusted networks only.
How severe is CVE-2020-29557?
CVE-2020-29557 is rated CRITICAL with a CVSS 3.1 score of 9.8. It enables unauthenticated remote code execution on the router, giving attackers full control over the device and all network traffic passing through it. The EPSS score of 0.89773 (99.57th percentile) and KEV listing confirm this is among the most exploited router vulnerabilities.
Need Help With Vulnerability Management?
Our security experts can help you prioritize and remediate vulnerabilities effectively.