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VulnerabilityPublished

CVE-2026-77987: GitHub Enterprise Server · Server-Side Request Forgery (SSRF)

Affects GitHub Enterprise ServerSource CVE Database V5

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Not known to be exploited · CVSS 9.3 Critical · fixed in 3.22.1 : patch GitHub Enterprise Server as a priority.

Data as of 5 Nov 2026, 23:24 UTC

CVSS 4.0 base score
9.3Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.8% chance of exploitation in 30 days – higher than 59% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.22.1, 3.21.6, 3.20.8 +3
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
GitHubEnterprise ServerAffected
  • >=3.22.0 <3.22.1
Fixed in
  • 3.22.1
GitHubEnterprise ServerAffected
  • >=3.21.0 <3.21.6
Fixed in
  • 3.21.6
GitHubEnterprise ServerAffected
  • >=3.20.0 <3.20.8
Fixed in
  • 3.20.8
GitHubEnterprise ServerAffected
  • >=3.19.0 <3.19.12
Fixed in
  • 3.19.12
GitHubEnterprise ServerAffected
  • >=3.18.0 <3.18.15
Fixed in
  • 3.18.15
GitHubEnterprise ServerAffected
  • >=3.17.0 <3.17.21
Fixed in
  • 3.17.21

AI-suggested

This vulnerability has been fixed in GitHub Enterprise Server versions 3.17.21, 3.18.15, 3.19.12, 3.20.8, 3.21.6, and 3.22.1. Users should upgrade to one of these patched versions immediately to remediate the issue. There are no vendor advisories indicating alternative mitigations or that no action is required.

Description

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.

References

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