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VulnerabilityPublished Updated

CVE-2026-77866: Slab safeurl · Server-Side Request Forgery (SSRF)

Affects Slab safeurlSource CVE Database V5

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Not known to be exploited · CVSS 9.0 Critical.

Data as of 30 Oct 2026, 20:25 UTC

CVSS 4.0 base score
9.0Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
SlabsafeurlAffected
  • >=0.1.0
Fixed in–
SlabsafeurlAffected
  • ≥ feabbd0a13f83028ab24b71710526e9da9841f70
Fixed in–
Hexsafeurlpkg:hex/safeurlOther threatsAffected
  • >=0.1.0
Fixed in–

CPE configurations (1)

  • cpe:2.3:a:slab:safeurl:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until a fix is available, deployments should consider using allowlist mode instead of blocklist mode to prevent bypass via IPv6 or non-IPv4-resolving hosts. Avoid relying solely on IPv4 blocklists for address validation.

Description

Server-Side Request Forgery (SSRF) vulnerability in Slab safeurl allows an attacker who controls a validated URL to reach internal network destinations the library is configured to block. Only IPv4 addresses are matched against the reserved ranges and the blocklist. Every other address is treated as matching nothing, so a destination that is rejected in its IPv4 form is accepted when written as an IPv6 address, IPv6 entries in the blocklist never match, and a host that resolves to no IPv4 address is accepted regardless of where it points. Deployments that rely on the allowlist instead are unaffected, because there an unmatched address is rejected. This issue affects safeurl: from 0.1.0 onward.

References

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