High severity · published Aug 5, 2026
CVE-2026-15996
Denial of service vulnerability in GitHub Enterprise Server allowed unauthenticated service disruption via deeply nested request parameters
7.5
CVSS
0.8%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 55% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ES
Enterprise Server · GitHub
3.17.0 through 3.17.15; 3.18.0 through 3.18.9; 3.19.0 through 3.19.6; 3.20.0 through 3.20.2 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-15996
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-15996
Product
https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.16
Product
https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.10
Product
https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.7
Product
https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.3
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