Gitea: Blind SSRF in OAuth2 avatar synchronization via unvalidated OIDC picture claim

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

3.1 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

EPSS

• CVE-2026-23603: 0.29% estimated exploitation activity in the next 30 days; percentile 21.59 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When [oauth2client] UPDATEAVATAR = true is enabled, Gitea fetches the avatar URL received from an OAuth2/OIDC provider using Go's default HTTP client. The URL comes from the user's OAuth/OIDC avatar value, commonly the OIDC picture claim. The affected code path calls http.Get(url) without applying outbound host or IP restrictions. A low-privileged user who can influence their own picture claim under an already-configured OAuth2/OIDC source can cause the Gitea server to make arbitrary outbound HTTP GET requests. This includes requests to loopback addresses, RFC 1918 private network addresses, and IPv4 link-local addresses such as 169.254.169.254. This is a blind SSRF by default. Impact can increase in deployments where the Gitea host can reach cloud metadata services, localhost-only services, or internal services that return valid image data. Details The vulnerable sink is in routers/web/auth/oauth.go: The caller is in routers/web/auth/oauthsigninsync.go: gothUser.AvatarURL is…

Published by the source

21 Jul 2026, 20:22 UTC

Last modified by the source

4 Oct 2026, 12:10 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-x77v-q46j-393g

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# Patch Next advisory brief: CVE-2026-23603

Advisory: Gitea: Blind SSRF in OAuth2 avatar synchronization via unvalidated OIDC picture claim
IDs: CVE-2026-23603, GHSA-x77v-q46j-393g
Record: https://patchnext.com/advisories/cve-2026-23603 (revision 1, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: code.gitea.io/gitea 1.27.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.gitea.io/gitea: affected < 1.27.0; fixed in 1.27.0

## Suggested inspection (read-only)
- Go code.gitea.io/gitea: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on code.gitea.io/gitea.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-x77v-q46j-393g (GitHub-reviewed advisory GHSA-x77v-q46j-393g lists affected ranges: Go code.gitea.io/gitea >=0 <1.27.0)

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