CVE-2026-49820: Go.probo.inc/probo Probo Has An Open Redirect Vulnerability

MODERATE
Advisory Identifier: GHSA-x7qq-m748-8p2c
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CVSS 4.7
CWE-601
Published
Advisory Summary

CVE-2026-49820 is a MODERATE (CVSS 4.7) probo has an open redirect vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Go.probo.inc/probo libraries in the Go ecosystem. The issue involves probo has an open redirect bypass via path normalization. Remediation is available by upgrading affected packages to version 0.204.0.

CVE-2026-49820 at a Glance

CVE Identifier CVE-2026-49820
GHSA Identifier GHSA-x7qq-m748-8p2c
Severity MODERATE
CVSS v3.1 Base Score 4.7
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Go.probo.inc/probo
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 4.7

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-49820

To remediate this vulnerability, upgrade all affected Go.probo.inc/probo dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

go.probo.inc/probo fixed: 0.204.0 
Upgrade go.probo.inc/probo to 0.204.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for go.probo.inc/probo

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-49820, inspect your project dependencies for Go.probo.inc/probo:

inspect dependencies for go.probo.inc/probo

Analyze the terminal output to locate any version of Go.probo.inc/probo in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.204.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Go.probo.inc/probo, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Probo's `saferedirect` package validates redirect URLs used across authentication flows (OIDC, SAML, session transfer, OAuth connectors, and trust-center magic links). The validator only inspected the second character of relative paths, so a URL like `/../\evil.com` passed validation because the second character is `.`. Go's `http.Redirect` normalizes this path to `/\evil.com` before setting the `Location` header. Browsers can interpret the backslash as a host separator and redirect the user to an external domain (`https://evil.com`), bypassing the intended same-origin restriction. This enables open-redirect phishing: an attacker can craft a `continue` parameter (or embed a malicious URL in a session-transfer token) that appears to originate from a trusted Probo domain but redirects victims elsewhere. ### Patches Fixed in `go.probo.inc/probo` by normalizing relative paths with `path.Clean` before validation, rejecting backslashes (including percent-encoded `%5c`) anywhere in the path, and re-checking the normalized result for protocol-relative and backslash prefixes. Self-hosted deployments should upgrade to **probod v0.194.1** or later. SaaS deployments on getprobo.com are patched. ### Workarounds No practical workaround for self-hosted installations. Upgrade to the patched release.

CVE-2026-49820 Affected Go.probo.inc/probo Versions

1 component(s)
Fixed Versions:
0.204.0
Product / Package Ecosystem Affected Versions Fixed Version
go.probo.inc/probo
golang/go.probo.inc/probo
Go
< 0.204.0
0.204.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/getprobo/probo/security/advisories/GHSA-x7qq-m748-8p2c
Go.probo.inc/probo Source Repository REPOSITORY
https://github.com/getprobo/probo
Go.probo.inc/probo Source Repository REPOSITORY
https://github.com/getprobo/probo/blob/main/SECURITY_NOTES.md

Frequently Asked Questions

What is CVE-2026-49820?
CVE-2026-49820 is a security vulnerability in Go.probo.inc/probo involving Probo has an open redirect bypass via path normalization under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Go.probo.inc/probo versions are affected?
Affected versions include releases prior to 0.204.0 across affected packages: go.probo.inc/probo.
What version fixes CVE-2026-49820?
Upgrading to 0.204.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is go.probo.inc/probo affected?
Yes, go.probo.inc/probo is affected in releases prior to 0.204.0. Upgrade your dependency to 0.204.0 or later.
What is the CVSS score of CVE-2026-49820?
CVE-2026-49820 has a CVSS v3.1 base score of 4.7 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N.
What CWE is associated with CVE-2026-49820?
CVE-2026-49820 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check Go dependencies for CVE-2026-49820?
Run the dependency tree command: 'inspect dependencies for go.probo.inc/probo'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x7qq-m748-8p2c",
  "modified" : "2026-06-30T18:31:50Z",
  "published" : "2026-06-30T18:31:50Z",
  "aliases" : [ "CVE-2026-49820" ],
  "summary" : "Probo has an open redirect bypass via path normalization",
  "details" : "### Impact\nProbo's `saferedirect` package validates redirect URLs used across authentication flows (OIDC, SAML, session transfer, OAuth connectors, and trust-center magic links). The validator only inspected the second character of relative paths, so a URL like `/../\\evil.com` passed validation because the second character is `.`. Go's `http.Redirect` normalizes this path to `/\\evil.com` before setting the `Location` header. Browsers can interpret the backslash as a host separator and redirect the user to an external domain (`https://evil.com`), bypassing the intended same-origin restriction. This enables open-redirect phishing: an attacker can craft a `continue` parameter (or embed a malicious URL in a session-transfer token) that appears to originate from a trusted Probo domain but redirects victims elsewhere.\n\n### Patches\nFixed in `go.probo.inc/probo` by normalizing relative paths with `path.Clean` before validation, rejecting backslashes (including\npercent-encoded `%5c`) anywhere in the path, and re-checking the normalized result for protocol-relative and backslash prefixes.\n\nSelf-hosted deployments should upgrade to **probod v0.194.1** or later.\n\nSaaS deployments on getprobo.com are patched.\n\n### Workarounds\nNo practical workaround for self-hosted installations. Upgrade to the patched release.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "go.probo.inc/probo"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.204.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/getprobo/probo/security/advisories/GHSA-x7qq-m748-8p2c"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/getprobo/probo"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/getprobo/probo/blob/main/SECURITY_NOTES.md"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-30T18:31:50Z",
    "nvd_published_at" : null
  }
}