CVE-2026-77987 (GCVE-0-2026-77987)

Vulnerability from cvelistv5 – Published: 2026-09-22 20:43 – Updated: 2026-09-23 15:26
VLAI
Title
GitHub Enterprise Server notebook viewer vulnerable to Server-side request forgery
Summary
A server-side request forgery (SSRF) vulnerability was identified in the notebook viewer of GitHub Enterprise Server. The notebook viewer validated the scheme and host of a user-supplied URL but did not validate the port, allowing requests to be directed to internal services listening on other ports of the same appliance. Response bodies were not returned to the requester, but response timing acted as an oracle that allowed instance secrets to be extracted character by character. An extracted secret could then be used in a separate interaction with an internal service to obtain remote code execution on the appliance. Exploitation required network access to the instance and was unauthenticated when private mode was disabled, or required any authenticated user when private mode was enabled. This vulnerability affected GitHub Enterprise Server versions 3.17 through 3.22 and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported through the GitHub Bug Bounty program.
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-23 15:26 UTC
CWE
  • CWE-918 - Server-Side Request Forgery (SSRF)
  • CWE-208 - Observable Timing Discrepancy
Assigner
GitHub_P CNA under the mitre root
CNA scorecard B 84/100 over 22 records in the last 180 days details
Impacted products
Vendor Product Version CPE status
GitHub Enterprise Server Affected: 3.17.0 , < 3.17.* (semver)
Affected: 3.18.0 , < 3.18.* (semver)
Affected: 3.19.0 , < 3.19.* (semver)
Affected: 3.20.0 , < 3.20.* (semver)
Affected: 3.21.0 , < 3.21.* (semver)
Affected: 3.22.0 , < 3.22.* (semver)
guessed Create a notification for this product.
Show details on NVD website

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                  "changes": [
                    {
                      "at": "3.21.6",
                      "status": "unaffected"
                    }
                  ],
                  "lessThan": "3.21.*",
                  "status": "affected",
                  "version": "3.21.0",
                  "versionType": "semver"
                },
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                  "changes": [
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                      "at": "3.22.1",
                      "status": "unaffected"
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                  ],
                  "lessThan": "3.22.*",
                  "status": "affected",
                  "version": "3.22.0",
                  "versionType": "semver"
                }
              ]
            }
          ],
          "credits": [
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              "lang": "en",
              "type": "finder",
              "value": "Seokchan Yoon"
            },
            {
              "lang": "en",
              "type": "finder",
              "value": "R31n"
            }
          ],
          "descriptions": [
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              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "A server-side request forgery (SSRF) vulnerability was identified in the notebook viewer of GitHub Enterprise Server. The notebook viewer validated the scheme and host of a user-supplied URL but did not validate the port, allowing requests to be directed to internal services listening on other ports of the same appliance. Response bodies were not returned to the requester, but response timing acted as an oracle that allowed instance secrets to be extracted character by character. An extracted secret could then be used in a separate interaction with an internal service to obtain remote code execution on the appliance. Exploitation required network access to the instance and was unauthenticated when private mode was disabled, or required any authenticated user when private mode was enabled. This vulnerability affected GitHub Enterprise Server versions 3.17 through 3.22 and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported through the GitHub Bug Bounty program.\u003cbr\u003e\u003cbr\u003e"
                }
              ],
              "value": "A server-side request forgery (SSRF) vulnerability was identified in the notebook viewer of GitHub Enterprise Server. The notebook viewer validated the scheme and host of a user-supplied URL but did not validate the port, allowing requests to be directed to internal services listening on other ports of the same appliance. Response bodies were not returned to the requester, but response timing acted as an oracle that allowed instance secrets to be extracted character by character. An extracted secret could then be used in a separate interaction with an internal service to obtain remote code execution on the appliance. Exploitation required network access to the instance and was unauthenticated when private mode was disabled, or required any authenticated user when private mode was enabled. This vulnerability affected GitHub Enterprise Server versions 3.17 through 3.22 and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported through the GitHub Bug Bounty program."
            }
          ],
          "impacts": [
            {
              "capecId": "CAPEC-664",
              "descriptions": [
                {
                  "lang": "en",
                  "value": "CAPEC-664 Server Side Request Forgery"
                }
              ]
            },
            {
              "capecId": "CAPEC-462",
              "descriptions": [
                {
                  "lang": "en",
                  "value": "CAPEC-462 Cross-Domain Search Timing"
                }
              ]
            }
          ],
          "metrics": [
            {
              "cvssV4_0": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "baseScore": 9.3,
                "baseSeverity": "CRITICAL",
                "exploitMaturity": "NOT_DEFINED",
                "privilegesRequired": "NONE",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "HIGH",
                "vulnIntegrityImpact": "HIGH",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "format": "CVSS",
              "scenarios": [
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                  "lang": "en",
                  "value": "GENERAL"
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              ]
            }
          ],
          "problemTypes": [
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              "descriptions": [
                {
                  "cweId": "CWE-918",
                  "description": "CWE-918 Server-Side Request Forgery (SSRF)",
                  "lang": "en",
                  "type": "CWE"
                },
                {
                  "cweId": "CWE-208",
                  "description": "CWE-208 Observable Timing Discrepancy",
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                  "type": "CWE"
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          "providerMetadata": {
            "dateUpdated": "2026-09-22T20:43:53.715Z",
            "orgId": "82327ea3-741d-41e4-88f8-2cf9e791e760",
            "shortName": "GitHub_P"
          },
          "references": [
            {
              "tags": [
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              "url": "https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.21"
            },
            {
              "tags": [
                "release-notes"
              ],
              "url": "https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.15"
            },
            {
              "tags": [
                "release-notes"
              ],
              "url": "https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.12"
            },
            {
              "tags": [
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              ],
              "url": "https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.8"
            },
            {
              "tags": [
                "release-notes"
              ],
              "url": "https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.6"
            },
            {
              "tags": [
                "release-notes"
              ],
              "url": "https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.1"
            }
          ],
          "source": {
            "discovery": "EXTERNAL"
          },
          "title": "GitHub Enterprise Server notebook viewer vulnerable to Server-side request forgery",
          "x_generator": {
            "engine": "Vulnogram 0.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "82327ea3-741d-41e4-88f8-2cf9e791e760",
        "assignerShortName": "GitHub_P",
        "cveId": "CVE-2026-77987",
        "datePublished": "2026-09-22T20:43:53.715Z",
        "dateReserved": "2026-08-21T18:51:48.052Z",
        "dateUpdated": "2026-09-23T15:26:58.923Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Events included in the timeline

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    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.