cbcvebase.
CVE-2026-20896
published 2026-07-03

CVE-2026-20896: Gitea Docker image versions up to and including 1.26.2 use REVERSE_PROXY_TRUSTED_PROXIES=* by default, allowing any source IP to impersonate a user when…

PriorityP193critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
ITWEXPLOITVulnCheck KEVInitial access
Exploited in the wild
EPSS
62.38%
99.1th percentile
Gitea Docker image versions up to and including 1.26.2 use REVERSE_PROXY_TRUSTED_PROXIES=* by default, allowing any source IP to impersonate a user when reverse-proxy authentication headers such as X-WEBAUTH-USER are enabled.

Affected

2 ranges
VendorProductVersion rangeFixed in
code.gitea.iogitea>= 0 < 1.26.31.26.3
giteagitea_open_source_git_server<= 1.26.2

Detection & IOCsextracted from sources · hover to see the quote

otherX-WEBAUTH-USER
filenameapp.ini
  • Alert on X-WEBAUTH-USER header values targeting known admin usernames such as 'admin' or 'gitea_admin', as these are the primary targets for privilege escalation via auto-registration.
  • Monitor Gitea app.ini for the presence of REVERSE_PROXY_TRUSTED_PROXIES=* combined with ENABLE_REVERSE_PROXY_AUTHENTICATION=true, which together constitute the vulnerable configuration.
  • ·Exploitation requires ENABLE_REVERSE_PROXY_AUTHENTICATION to be explicitly set to true by an admin; instances where reverse-proxy authentication is not enabled are not directly exploitable via this header-injection path.
  • ·The safe/documented default for REVERSE_PROXY_TRUSTED_PROXIES is '127.0.0.0/8,::1/128' (localhost only), but the official Gitea Docker image hard-codes '*' instead, overriding this safe default for all Docker-based deployments up to and including 1.26.2.
  • ·Auto-registration being enabled amplifies impact: an attacker sending an admin username via X-WEBAUTH-USER will be automatically registered and granted admin privileges if the account does not yet exist.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vulncheck9.8CRITICAL
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