CVE-2026-71271: CWE-918 in usememos memos
Memos' webhook URL validation, isReservedIP() (internal/webhook/validate.go), checks a candidate IP against a reservedCIDRs list that omits 0.0.0.0/8 and never calls ip.IsUnspecified() — unlike the correctly implemented sibling function isInternalIP() in internal/httpgetter/html_meta.go, which does. Because Linux redirects connections to 0.0.0.0 to loopback (127.0.0.1), an attacker registering a webhook URL of http://0.0.0.0:PORT/ bypasses the reserved-IP check and causes the Memos server to make outbound HTTP requests to its own loopback interface, exposing internal-only services.
AI Analysis
Technical Summary
The vulnerability arises because the isReservedIP() function in memos' webhook URL validation does not include the 0.0.0.0/8 range in its reservedCIDRs list and does not call ip.IsUnspecified(), unlike the correctly implemented isInternalIP() function. On Linux systems, connections to 0.0.0.0 are redirected to the loopback address 127.0.0.1. An attacker can exploit this by registering a webhook URL with the IP 0.0.0.0, causing the memos server to make HTTP requests to its own loopback interface, potentially exposing internal services that should not be accessible externally.
Potential Impact
Successful exploitation allows an attacker with limited privileges to bypass IP-based restrictions on webhook URLs and cause the memos server to send HTTP requests to internal-only services on the loopback interface. This can lead to unauthorized access or information disclosure of internal services. The CVSS score of 8.5 indicates high severity with high confidentiality impact, low integrity impact, and no availability impact.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, users should avoid registering webhook URLs that use the IP 0.0.0.0 or similar unspecified addresses. Monitoring and restricting webhook URL inputs to exclude unspecified or loopback addresses can help mitigate the risk.
CVE-2026-71271: CWE-918 in usememos memos
Description
Memos' webhook URL validation, isReservedIP() (internal/webhook/validate.go), checks a candidate IP against a reservedCIDRs list that omits 0.0.0.0/8 and never calls ip.IsUnspecified() — unlike the correctly implemented sibling function isInternalIP() in internal/httpgetter/html_meta.go, which does. Because Linux redirects connections to 0.0.0.0 to loopback (127.0.0.1), an attacker registering a webhook URL of http://0.0.0.0:PORT/ bypasses the reserved-IP check and causes the Memos server to make outbound HTTP requests to its own loopback interface, exposing internal-only services.
CVSS v3.1
Score 8.5high
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises because the isReservedIP() function in memos' webhook URL validation does not include the 0.0.0.0/8 range in its reservedCIDRs list and does not call ip.IsUnspecified(), unlike the correctly implemented isInternalIP() function. On Linux systems, connections to 0.0.0.0 are redirected to the loopback address 127.0.0.1. An attacker can exploit this by registering a webhook URL with the IP 0.0.0.0, causing the memos server to make HTTP requests to its own loopback interface, potentially exposing internal services that should not be accessible externally.
Potential Impact
Successful exploitation allows an attacker with limited privileges to bypass IP-based restrictions on webhook URLs and cause the memos server to send HTTP requests to internal-only services on the loopback interface. This can lead to unauthorized access or information disclosure of internal services. The CVSS score of 8.5 indicates high severity with high confidentiality impact, low integrity impact, and no availability impact.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, users should avoid registering webhook URLs that use the IP 0.0.0.0 or similar unspecified addresses. Monitoring and restricting webhook URL inputs to exclude unspecified or loopback addresses can help mitigate the risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- TuranSec
- Date Reserved
- 2026-08-05T12:23:34.967Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a7336e4bf8831d539ed9148
Added to database: 08/05/2026, 13:13:08 UTC
Last enriched: 08/05/2026, 13:31:26 UTC
Last updated: 08/05/2026, 18:47:02 UTC
Views: 4
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