{"id":"CVE-2026-77972","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-77972","generatedAt":"2026-09-20T15:01:46.752Z","title":"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.","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.\n\nValidation 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.\n\nThis issue affects safeurl: from 0.1.0 onward.","published":"2026-09-15T16:17:24.000Z","lastModified":"2026-09-16T20:38:34.000Z","status":"Awaiting Analysis","sourceIdentifier":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","cvss":{"version":"4.0","score":9,"severity":"CRITICAL","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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M"},"cwe":["CWE-367"],"affected":[],"epss":{"score":0.00317,"percentile":0.24843,"date":"2026-09-19","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.32%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://cna.erlef.org/cves/CVE-2026-77972.html","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://github.com/slab/safeurl-elixir/commit/feabbd0a13f83028ab24b71710526e9da9841f70","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-77972","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-77972","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}