---
cve: "CVE-2026-77972"
severity: "CRITICAL"
cvss: 9.0
epss: "0.3%"
vendor: "Slab"
kev: false
exploited: false
published: "2026-09-15 16:17:24"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-20T19:54:45+02:00"
---

# CVE-2026-77972

> 9.0 CRITICAL · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- feabbd0a13f83028ab24b71710526e9da9841f70 (Commit)

## Referenzen

- <https://cna.erlef.org/cves/CVE-2026-77972.html>
- <https://osv.dev/vulnerability/EEF-CVE-2026-77972>
- <https://github.com/slab/safeurl-elixir/commit/feabbd0a13f83028ab24b71710526e9da9841f70>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-77972) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_