CVE-2026-19118Network attack vector

Authenticated code execution via concurrent upload replacement

Published Sep 1, 2026 · Updated Sep 2, 2026

TOCTOU race in GitHub Enterprise Server allows remote authenticated users to execute arbitrary code via concurrent repository uploads. The upload path validates content and processes it later, allowing a concurrent request to replace the validated upload with attacker-controlled content. Exploitation requires repository write access and precise request timing; successful exploitation runs arbitrary code on the instance.

CVSS severity7.7
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

TOCTOU race in GitHub Enterprise Server allows remote authenticated users to execute arbitrary code via concurrent repository uploads. The upload path validates content and processes it later, allowing a concurrent request to replace the validated upload with attacker-controlled content. Exploitation requires repository write access and precise request timing; successful exploitation runs arbitrary code on the instance.

The record

CVE
CVE-2026-19118
Published
Sep 1, 2026
Updated
Sep 2, 2026
Vendor
Twitter
Product
GitHub Enterprise Server
Classifications
CWE-367, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.17.0 <=3.17.19 changes=[{"at":"3.17.20","status":"unaffected"}]
  2. Affected versionversion=3.18.0 <=3.18.13 changes=[{"at":"3.18.14","status":"unaffected"}]
  3. Affected versionversion=3.19.0 <=3.19.10 changes=[{"at":"3.19.11","status":"unaffected"}]
  4. Affected versionversion=3.20.0 <=3.20.6 changes=[{"at":"3.20.7","status":"unaffected"}]
  5. Affected versionversion=3.21.0 <=3.21.4 changes=[{"at":"3.21.5","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Twitter · GitHub Enterprise Serverversion=3.17.0 <=3.17.19 changes=[{"at":"3.17.20","status":"unaffected"}]; version=3.18.0 <=3.18.13 changes=[{"at":"3.18.14","status":"unaffected"}]; version=3.19.0 <=3.19.10 changes=[{"at":"3.19.11","status":"unaffected"}]; version=3.20.0 <=3.20.6 changes=[{"at":"3.20.7","status":"unaffected"}]; version=3.21.0 <=3.21.4 changes=[{"at":"3.21.5","status":"unaffected"}]

Published CVSS scores

7.7GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo