How severe is CVE-2026-8034?

CVE-2026-8034 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-8034 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-8034?

CVE-2026-8034 affects Github Enterprise Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-8034?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-8034 have an EU (EUVD) identifier?

Yes. CVE-2026-8034 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28464.

When was CVE-2026-8034 published?

CVE-2026-8034 was published on 2026-05-07 and last updated on 2026-06-17.

CVE-2026-8034

CVE-2026-8034 is a critical-severity vulnerability in Github Enterprise Server with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-436.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 7.9
EPSS exploit prediction: 0% (30th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-28464
Weakness: CWE-436
Affected product: Github Enterprise Server
Published: 2026-05-07
Last modified: 2026-06-17

Description

A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook viewer that allowed an attacker to access internal services by exploiting URL parser confusion between the validation layer and the HTTP request library. The hostname validation used a different URL parser than the request library, enabling a crafted URL to pass validation while directing the request to an unintended host. Exploitation required network access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.16.18, 3.17.15, 3.18.9, 3.19.6, and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.

Frequently asked questions

What is CVE-2026-8034?: A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook viewer that allowed an attacker to access internal services by exploiting URL parser confusion between the validation layer and the HTTP request library. The hostname validation used a different URL parser than the request library, enabling a crafted URL to pass validation while directing the request to an unintended host. Exploitation required network access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.16.18, 3.17.15, 3.18.9, 3.19.6, and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.
How severe is CVE-2026-8034?: CVE-2026-8034 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-8034 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-8034?: CVE-2026-8034 affects Github Enterprise Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-8034?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-8034 have an EU (EUVD) identifier?: Yes. CVE-2026-8034 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28464.
When was CVE-2026-8034 published?: CVE-2026-8034 was published on 2026-05-07 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:github:enterprise_server:*:*:*:*:*:*:*:*

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