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NVD / CVE Program· CNA GitHub_P

CVE-2026-5921: Server-Side Request Forgery in GitHub Enterprise Server allowed extraction of sensitive environment variables via timing side-channel…

HighCVSS 8.9 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 35/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.42% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: GitHub Enterprise Server 3.14.26, 3.15.21, 3.16.17.

Low priority for now. Upgrade to GitHub Enterprise Server 3.14.26, 3.15.21, 3.16.17 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the notebook viewer followed HTTP redirects without revalidating the destination host, enabling an unauthenticated SSRF to internal services. By chaining this with regex filter queries against an internal API and measuring response time differences, an attacker could infer secret values character by character. Exploitation required that private mode be disabled and that the attacker be able to chain the instance's open redirect endpoint through an external redirect to reach internal services. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5, and 3.20.1. This vulnerability was reported via the GitHub Bug Bounty program.

Published
Apr 21, 2026
Updated
Oct 26, 2026
EPSS
0.4% · 37th percentile

Report tools

JSON

Action score

35

Monitor

Low priority for now.

CVSS
35 / 40 · 8.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_P
8.9
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L/E:P

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-5921

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
githubenterprise server

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_P). Independent of NVD's CPE analysis and usually ahead of it.

  • GitHub Enterprise Server

    • 3.14.0 and later · before 3.14.26affected · semverfixed in 3.14.26
    • 3.15.0 and later · before 3.15.21affected · semverfixed in 3.15.21
    • 3.16.0 and later · before 3.16.17affected · semverfixed in 3.16.17
    • 3.17.0 and later · before 3.17.14affected · semverfixed in 3.17.14
    • 3.18.0 and later · before 3.18.8affected · semverfixed in 3.18.8
    • 3.19.0 and later · before 3.19.5affected · semverfixed in 3.19.5
    • 3.20.0 and later · before 3.20.1affected · semverfixed in 3.20.1
Affected versions · NVD (7)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • github enterprise serverbefore 3.14.26
  • github enterprise server3.15.0 and later · before 3.15.21
  • github enterprise server3.16.0 and later · before 3.16.17
  • github enterprise server3.17.0 and later · before 3.17.14
  • github enterprise server3.18.0 and later · before 3.18.8
  • github enterprise server3.19.0 and later · before 3.19.5
  • github enterprise server3.20.0

Same product

github: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-0200Unsafe Reflection in Github Enterprise Server leading to Command Injection
    61This week
  • CVE-2024-0507Privilege Escalation by Code Injection in the Management Console in GitHub Enterprise Server
    55Plan
  • CVE-2026-3854Remote code execution via git push option injection in GitHub Enterprise Server
    47Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-5512Apr 21, 2026 · Improper authorization vulnerability in GitHub Enterprise Server allowed disclosure of private repository names via mobile upload policy…
    21Monitor
  • ← EarlierCVE-2026-5845Apr 21, 2026 · Improper authorization fallback allows scoped user-to-server token installation escape in GitHub Enterprise Server
    28Monitor
  • Later →CVE-2026-6736May 7, 2026 · Authentication bypass vulnerability in GitHub Enterprise Server allowed creation of local user accounts bypassing the configured external identity provider
    25Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
GitHub Enterprise Server3.14.26Vendor (CNA)
GitHub Enterprise Server3.15.21Vendor (CNA)
GitHub Enterprise Server3.16.17Vendor (CNA)
GitHub Enterprise Server3.17.14Vendor (CNA)
GitHub Enterprise Server3.18.8Vendor (CNA)
GitHub Enterprise Server3.19.5Vendor (CNA)
GitHub Enterprise Server3.20.1Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-931235 days apartServer-Side Request Forgery vulnerability in GitHub Enterprise Server allowed access to internal services via path traversal in upload endpoint
    39Monitor
  • CVE-2026-96890168 days apartServer-Side Request Forgery vulnerability was identified in GitHub Enterprise Server that allowed requests to attacker-controlled internal hosts
    34Monitor
  • CVE-2026-18730133 days apartServer-side request forgery vulnerability in GitHub Enterprise Server Manage API leaked a replayable gateway-agent bearer token
    32Monitor
  • CVE-2026-76851133 days apartServer-Side Request Forgery vulnerability in GitHub Enterprise Server allowed remote code execution via network access from pre-receive hooks to internal…
    30Monitor
  • CVE-2026-860635 days apartServer-Side Request Forgery in GitHub Enterprise Server via Advisory Package URL Endpoint
    28Monitor

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Not on record for this CVE: EPSS history · patch commit or PR link.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-918 · Server-Side Request Forgery (SSRF)

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L/E:P/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-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records