CVE-2026-77866

CRITICALPre-NVD 9.09.0—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.0 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 61% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 4 sources updated this week
9.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.0Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.0
EG Score
9.0(medium)
EG Risk
45(Track)
EG Risk 45/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity90% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
39%
KEV
Not listed

Published

September 15, 2026

Last Modified

September 16, 2026

Advisory Details (3)

Auto-updated Sep 15, 2026
Patch available. Sources: github_commit.
github_commit Patch Available

commit feabbd0a13f8 (slab/safeurl-elixir)

Patch available: slab/safeurl-elixir v0.2.0 (contains commit feabbd0a13f8)

https://github.com/slab/safeurl-elixir/commit/feabbd0a13f83028ab24b71710526e9da9841f70
generic

OSV - Open Source Vulnerabilities

https://osv.dev/vulnerability/EEF-CVE-2026-77866
generic

CVE-2026-77866

https://cna.erlef.org/cves/CVE-2026-77866.html

Vendor Advisories for CVE-2026-77866(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Hex(1)
PackageVulnerable rangeFixed inDependents
safeurl0.1.0, 0.2.0, 0.3.0, 0.3.1, 1.0.0——

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 28× in last 7d / 28× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-19 04:14 UTCGHSA enrichment
  2. 2026-09-19 00:13 UTCGHSA enrichment
  3. 2026-09-18 20:12 UTCEG score recompute
  4. 2026-09-18 20:12 UTCGHSA enrichment
  5. 2026-09-18 19:28 UTCEPSS rescore
  6. 2026-09-18 16:08 UTCGHSA enrichment
  7. 2026-09-18 11:54 UTCGHSA enrichment
  8. 2026-09-18 07:52 UTCGHSA enrichment
  9. 2026-09-18 03:51 UTCGHSA enrichment
  10. 2026-09-17 23:49 UTCEG score recompute
  11. 2026-09-17 23:49 UTCGHSA enrichment
  12. 2026-09-17 19:21 UTCGHSA enrichment
  13. 2026-09-17 13:13 UTCGHSA enrichment
  14. 2026-09-17 09:11 UTCGHSA enrichment
  15. 2026-09-17 05:09 UTCGHSA enrichment
  16. 2026-09-17 01:08 UTCGHSA enrichment
  17. 2026-09-16 21:07 UTCGHSA enrichment
  18. 2026-09-16 17:55 UTCEG score recompute
  19. 2026-09-16 17:55 UTCGHSA enrichment
  20. 2026-09-16 14:08 UTCEPSS rescore
  21. 2026-09-16 12:55 UTCGHSA enrichment
  22. 2026-09-16 08:53 UTCGHSA enrichment
  23. 2026-09-16 04:51 UTCGHSA enrichment
  24. 2026-09-16 00:49 UTCGHSA enrichment
  25. 2026-09-15 20:47 UTCGHSA enrichment
Show 3 more
  1. 2026-09-15 16:32 UTCEG score recompute
  2. 2026-09-15 15:43 UTCEG score recompute
  3. 2026-09-15 15:42 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-77866?
CVE-2026-77866 is a critical vulnerability published on September 15, 2026. 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…
When was CVE-2026-77866 disclosed?
CVE-2026-77866 was first published in the National Vulnerability Database on September 15, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-77866 actively exploited?
CVE-2026-77866 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 60.9% of all scored CVEs.
What is the CVSS score of CVE-2026-77866?
CVE-2026-77866 has a CVSS v3 base score of 9.0 (NVD).
How do I remediate CVE-2026-77866?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77866, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-77866

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