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JWT leak via Open Redirect in Programmatic access

Moderate severity GitHub Reviewed Published Mar 31, 2021 in pomerium/pomerium • Updated Oct 2, 2023

Package

gomod github.com/pomerium/pomerium (Go)

Affected versions

< 0.13.4

Patched versions

0.13.4

Description

Impact

Using programmatic access on protected sites, one can get a signed login URL with pomerium_redirect_uri set to an arbitrary URL. Then, if the user has already logged into Pomerium, they will be redirected to the specified pomerium_redirect_uri with a JWT attached. This allows an outside attacker to get a signed login URL that, upon visiting it, will redirect a victim to the attacker’s site. This creates an issue of Open Redirect and, more seriously, JWT leakage.

With a leaked JWT, the attacker will be able to unveil the victim’s identity (.e.g. email address) by supplying the JWT to the authenticate service or verify.pomerium.com. In addition, if an application integrating Pomerium only verifies the iss claim and others but not the aud claim, the attacker will be able to access it as the victim.

Specific Go Packages Affected

github.com/pomerium/pomerium/proxy

Patches

Patched in Pomerium v0.13.4

For more information

If you have any questions or comments about this advisory

References

@travisgroth travisgroth published to pomerium/pomerium Mar 31, 2021
Reviewed May 20, 2021
Published to the GitHub Advisory Database May 21, 2021
Last updated Oct 2, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N

EPSS score

0.078%
(35th percentile)

CVE ID

CVE-2021-29651

GHSA ID

GHSA-35vc-w93w-75c2

Source code

No known source code

Credits

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