Summary
Open WebUI: DNS Rebinding SSRF Bypass
Open WebUI vetted user-supplied URLs by resolving the hostname once and rejecting private, loopback and link-local addresses, then let the HTTP client resolve that hostname again at connect time. An attacker who controls the authoritative DNS for a hostname they submit can answer with a public address during the check and an internal one at connect, so the fetch reaches an address the check was meant to block. Every user-reachable fetch gated by that check was affected, and most of them hand the internal response back to the attacker.
Preconditions
- An account on the instance. No admin rights and no non-default configuration.
- Control of the authoritative DNS for a hostname the attacker submits, serving a TTL of 0 and alternating answers.
- One of the affected entry points: URL ingest for retrieval, an
image_urlin a chat completion, image editing, or the OAuth profile-picture fetch. - The OAuth path additionally needs OAuth login configured and a picture claim (
OAUTH_PICTURE_CLAIM, defaultpicture) the user can influence, which is the case on self-service OIDC providers and providers with a user-editable avatar URL. On an existing account it also needsOAUTH_UPDATE_PICTURE_ON_LOGIN, which is off by default. Deployments without OAuth are not affected on that path; the other paths need no configuration at all.
Root cause
Affected components:
- retrieval web loader (
SafeWebBaseLoader) - retrieval content probe (
get_content_from_url) - chat image fetch (
get_image_base64_from_url) - image edit fetch (
load_url_image) - OAuth profile-picture fetch (
_process_picture_url)
The URL check resolved the hostname and inspected the resulting IP, but nothing tied that decision to the connection that followed: the HTTP client resolved the name again on its own, and the second answer was never inspected. The check was therefore an opinion about a past lookup rather than a constraint on the actual connection, which is what a rebinding DNS server defeats. The first connection-layer guard covered only the retrieval loader, leaving the sibling probe, image and OAuth fetches on default clients until each was reported in turn.
Credits
- @rezaduty, the rebinding time-of-check/time-of-use bypass and the retrieval loader path.
- @nikchillz, the retrieval content-probe path.
- @dhyabi2, the chat
image_urlpath, where the internal response is read back through the vision model. - @geo-chen, the image-edit path.
- @bogdancherniy11-sudo, the OAuth profile-picture path, where the rebind also discloses the forwarded OAuth access token.
Impact
The server can be made to issue requests to addresses only it can reach: cloud instance metadata such as 169.254.169.254, loopback-bound admin APIs, and internal network services. The response comes back to the attacker on most paths, as document content on the retrieval path, described by the vision model on the chat image path, and base64-encoded into the profile picture on the OAuth path; the image-edit path is blind. On the OAuth path the server also forwards the OAuth access token as a Bearer header to the fetched URL, so a rebind hands that token to the internal target. On a cloud host with IMDSv1 reachable this is enough to take instance IAM credentials.
Exploitation depends on winning the gap between the two resolutions, which the attacker influences but does not fully control. Admin-configured image-generation backends and the shared session pool are not affected and deliberately keep the default client, since an administrator may legitimately point those at an internal host.
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2026-54020 has a CVSS score of 6.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.11.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in v0.11.0 (#24759, #25775, #25960, #26699). The check now happens at the connection layer instead of ahead of it: a requests transport adapter resolves the hostname once and connects to that same validated address, and an aiohttp resolver applies the same global-IP check, exposed as a one-off session used by every fetch behind the URL check. Upgrading to v0.11.0 resolves this with no configuration change.
Frequently Asked Questions
- What is CVE-2026-54020? CVE-2026-54020 is a medium-severity server-side request forgery (SSRF) vulnerability in open-webui (pip), affecting versions <= 0.10.2. It is fixed in 0.11.0. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- How severe is CVE-2026-54020? CVE-2026-54020 has a CVSS score of 6.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of open-webui are affected by CVE-2026-54020? open-webui (pip) versions <= 0.10.2 is affected.
- Is there a fix for CVE-2026-54020? Yes. CVE-2026-54020 is fixed in 0.11.0. Upgrade to this version or later.
- Is CVE-2026-54020 exploitable, and should I be worried? Whether CVE-2026-54020 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-54020 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-54020? Upgrade
open-webuito 0.11.0 or later.