GitHubCVE-2026-15996
GitHub Enterprise Server: denial of service
Medium6.6CVE-2026-15996 · Published Aug 5, 2026 · updated Aug 18, 2026
A denial of service vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to cause excessive CPU consumption and exhaust the pool of request-handling worker processes by sending a crafted form-encoded HTTP POST request containing deeply nested parameters. Because request parameters were parsed before routing and authentication, any POST endpoint could be used to trigger the condition, which could render the instance unresponsive. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.3, 3.19.7, 3.18.10, and 3.17.16.
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| Enterprise Server Product | >= 3.17.0, <= 3.17.15 | No fix yet |
| >= 3.18.0, <= 3.18.9 | No fix yet | |
| >= 3.19.0, <= 3.19.6 | No fix yet | |
| >= 3.20.0, <= 3.20.2 | No fix yet |
Details and references
- CVSS 4.0
- CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/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
- Severity from
- the vendor (its own CVE record or advisory)
- Weakness
- CWE-674
- www.cve.org/CVERecord?id=CVE-2026-15996
- nvd.nist.gov/vuln/detail/CVE-2026-15996
- docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.16
- docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.10
- docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.7
- docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.3
More GitHub advisories
All GitHub| Date | Advisory | Severity | Fixed in |
|---|---|---|---|
| Aug 8 | gh-aw: safe-output validator forwards undeclared agent fields to the appliers (scope escape / mass assignment) | Critical9.1 | v0.86.1 |
| Aug 7 | gh-aw: unauthenticated prompt-injection to code execution in the shipped ai-moderator workflow | Medium6.5 | v0.86.1 |
| Aug 7 | command injection in compiled workflow via unsanitized `sandbox.mcp.env` exports | Critical9.6 | v0.86.0 |
| Aug 7 | gh-aw: URL allowlist bypass via userinfo @ in the content sanitizer (exfiltration channel) | Medium6.8 | v0.86.0 |
| Aug 6 | Safe-outputs config emitter: JSON injection via templated values despite env-var indirection | High8.5 | v0.78.0 |
| Aug 5 | GitHub Enterprise Server: path traversal | High8.8 | No fix yet |