CVE-2026-55438
MediumCVSS 5.8Exploitation Probability (EPSS)
Low risk13th percentile - higher than 13% of all known CVEs
Summary
In Coder prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, the subdomain-based workspace app proxy allowed bypassing the same-owner CORS check. When a workspace-name subdomain segment parsed as a UUID, the workspace was resolved by ID without verifying the URL's username matched the real owner, while the CORS middleware trusted the unverified username in the hostname.
Risk Assessment
The risk involves potential data theft or unauthorized access to the victim's workspaces if an attacker tricks an authenticated user into visiting a crafted app URL. Practical exploitation requires subdomain app routing (wildcard hostname) enabled.
Recommendation
Immediately update Coder to versions 2.29.17, 2.32.7, 2.33.8, or 2.34.2, which include a fix that validates the subdomain username against the resolved workspace's actual owner. No known workarounds are available.
Other vulnerabilities in Coder
See all- CVE-2026-46354Critical
In Coder prior to versions 2.24.5, 2.29.13, 2.30.8, 2.31.12, 2.32.2, and 2.33.3, the `azureidentity.Validate()` function does not verify the PKCS#7 signature, only checking that the signer certificate chains to a trusted Azure CA. An attacker can embed a legitimate Azure certificate alongside arbitrary content, e.g., `{"vmId":"<target>"}`, and the forged `vmId` will be accepted, returning the victim workspace agent's session token.
- CVE-2026-55437Medium
In Coder prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, the `AgentLogLine` dashboard component used `ansi-to-html` without `escapeXML: true` and inserted the result via `dangerouslySetInnerHTML`, causing HTML embedded in agent logs to be rendered as live markup. Server-side sanitization did not neutralize HTML metacharacters.
- CVE-2026-55436High
In Coder from version 2.30.0 to 2.32.7, 2.33.8, and 2.34.2, the AI Bridge Proxy (`aibridgeproxyd`) created a goproxy server whose default transport set `InsecureSkipVerify: true`, accepting any TLS certificate for outbound HTTPS to the Coder access URL. This allows man-in-the-middle attacks.
- CVE-2026-55433Medium
In Coder prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, the devcontainer recreate endpoint only checked `ActionRead` on the workspace, missing an `ActionUpdate` check before triggering a destructive rebuild. An attacker with low privileges and workspace access could exploit this for unauthorized rebuilds.
- CVE-2026-55432Medium
In Coder prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, the `CreateSubAgent` RPC did not validate a requested app sharing level against the template's `MaxPortSharingLevel` before persisting workspace apps, letting a workspace owner exceed the administrator's configured maximum.
- CVE-2026-55431High
A vulnerability in Coder CLI allows session token theft by opening a malicious workspace app URL. An attacker (template author) can configure an external workspace app that, when `coder open app` is executed, substitutes the session token in the URL and opens it in the victim's browser.
- CVE-2026-55430Medium
A vulnerability in Coder allows an attacker to redirect traffic from the workspace app proxy to an arbitrary host via the X-Forwarded-Host header. The issue occurs when subdomain app routing (wildcard hostname) is enabled, a victim visits the attacker's shared app, and the upstream proxy does not strip this header.
- CVE-2026-55429High
In Coder prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, `UpsertWorkspaceApp` overwrites an existing app entry and `insertAgentApp` accepts the app ID from the `CompleteJob` payload without verifying it belongs to the workspace being built. This allows cross-workspace agent reassignment, requiring elevated privileges of a template author or external provisioner operator.
- CVE-2026-55428High
In Coder prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, the tailnet coordinator does not validate the AllowedIPs field supplied by agents, allowing an agent to spoof another UUID and intercept network traffic. This vulnerability lets unauthorized agents inject arbitrary routes into WireGuard peer configurations, potentially enabling man-in-the-middle attacks.
- CVE-2026-55427High
A vulnerability in Coder allows injection of arbitrary SSH configuration into the user's ~/.ssh/config via unsanitized HostnameSuffix and SSHConfigOptions values supplied by the server. Exploitation requires control over the Coder server (malicious deployment, MITM attack, or admin access).
Original NVD description (English source)
Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2, Coder's subdomain-based workspace app proxy allowed the same-owner CORS check to be bypassed. When a workspace-name subdomain segment parsed as a UUID, the workspace was resolved by ID without confirming the URL's username matched the real owner, while the CORS middleware trusted the unverified username in the hostname. Practical exploitation requires subdomain app routing (wildcard hostname) enabled and a victim who visits the attacker's crafted app URL while authenticated. The fix in versions 2.29.17, 2.32.7, 2.33.8, and 2.34.2 validates the subdomain username against the resolved workspace's actual owner and bases the same-owner CORS decision on the authoritative owner identity. No known workarounds are available.