CVE-2026-77866

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

• ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
• AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.48% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 41.1% of scored records. A rank, not a probability.

NVD base score

9.0 (CVSS v4.0), scored by the NVD independently of the CNA.

NVD CVSS vector

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

NVD analysis status

Awaiting Analysis. NVD last modified this record on 2026-09-21.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2026-09-15 15:38Z1 MO AGO

Last updated

2026-09-21 18:44Z1 MO AGO

Reserved

2026-08-30

Assigning CNA

EEF

Record state

PUBLISHED

Severity

Critical (CVSS 9.0)

CNA CVSS vector

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

Weaknesses

• CWE-636Not Failing Securely ('Failing Open')Class
• CWE-918Server-Side Request Forgery (SSRF)Base

Data version

5.2

Document digest

4c35a07dcf127ccd822015226176595ee6c022d6a58c477ddc7f2d49d08c5c98

• cna.erlef.orgEEF CNA record for CVE-2026-77866https://cna.erlef.org/cves/CVE-2026-77866.htmlrelatedthird-party-advisory
• osv.devOSV record EEF-CVE-2026-77866https://osv.dev/vulnerability/EEF-CVE-2026-77866related
• github.comIntroducing commit feabbd0 in slab/safeurl-elixirhttps://github.com/slab/safeurl-elixir/commit/feabbd0a13f83028ab24b71710526e9da9841f70related