Description
Time-of-check Time-of-use (TOCTOU) Race Condition in Slab safeurl allows an attacker who controls a hostname's DNS responses to reach internal network destinations that validation rejected.

Validation returns a verdict and not the address it approved, so the HTTP clients the library ships receive the original hostname and resolve it a second time when the request is made. An attacker who controls the authoritative DNS for a name can answer the first lookup with a permitted address and the second with a blocked one, and the request then reaches a destination validation never approved. The same window opens without an attacker whenever a name legitimately resolves to different addresses across lookups, such as short record lifetimes or rotation between several addresses.

This issue affects safeurl: from 0.1.0 onward.
Published: 2026-09-15
Score: 9 Critical
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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History

Tue, 15 Sep 2026 15:45:00 +0000

Type Values Removed Values Added
Description Time-of-check Time-of-use (TOCTOU) Race Condition in Slab safeurl allows an attacker who controls a hostname's DNS responses to reach internal network destinations that validation rejected. Validation returns a verdict and not the address it approved, so the HTTP clients the library ships receive the original hostname and resolve it a second time when the request is made. An attacker who controls the authoritative DNS for a name can answer the first lookup with a permitted address and the second with a blocked one, and the request then reaches a destination validation never approved. The same window opens without an attacker whenever a name legitimately resolves to different addresses across lookups, such as short record lifetimes or rotation between several addresses. This issue affects safeurl: from 0.1.0 onward.
Title safeurl validated address is not bound to the request, allowing DNS rebinding
First Time appeared Slab
Slab safeurl
Weaknesses CWE-367
CPEs cpe:2.3:a:slab:safeurl:*:*:*:*:*:*:*:*
Vendors & Products Slab
Slab safeurl
References
Metrics cvssV4_0

{'score': 9, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-09-15T15:37:49.948Z

Reserved: 2026-08-24T15:45:02.127Z

Link: CVE-2026-77972

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-15T16:17:24.290

Modified: 2026-09-15T16:17:24.290

Link: CVE-2026-77972

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses