CVE-2026-77972 safeurl validated address is not bound to the request, allowing DNS rebinding
An attacker can bypass SSRF protections in the safeurl library via DNS rebinding, allowing access to internal network resources.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-77972?
CVE-2026-77972 is a critical server-side request forgery vulnerability in Slab safeurl, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-367
Which versions are affected by CVE-2026-77972?
1 open source package ship an affected version, including safeurl.
| Package | Affected | Fixed in |
|---|---|---|
safeurl Hex | From 0.1.0 | None |
How do I fix CVE-2026-77972?
No fix has been published for CVE-2026-77972 yet. Limit exposure of the affected software until one is available.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-77972 being exploited?
There is no known exploitation of CVE-2026-77972 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-77972, GHSA-pqwh-q74p-w7h4.