OPeNDAP Hyrax SSRF Leaks Earthdata Tokens
A flaw in OPeNDAP Hyrax lets attackers bypass host allowlists via HTTP redirects, enabling SSRF and leaking Earthdata authentication headers.
CERT/CC disclosed CVE-2026-16637, a server-side request forgery vulnerability in OPeNDAP Hyrax, an open-source data server widely used for scientific dataset access via the OPeNDAP protocol. The flaw stems from Hyrax's failure to re-validate HTTP redirect (3xx) destinations against its configured AllowedHosts allowlist, allowing a remote attacker to redirect requests to internal or otherwise restricted systems that should not be reachable from the internet.
Compounding the SSRF issue, when the redirect is followed, Hyrax may forward legacy Earthdata identification headers—specifically User-Id and the reusable Echo-Token—to the attacker-controlled destination, even though the primary authorization token is correctly stripped. An unauthenticated attacker could leverage this to probe internal network services, and if a legitimate authenticated user's session is exploited, the attacker could harvest the user's Earthdata identifier and legacy token to impersonate them and access protected scientific datasets.
No patch is currently available; OPeNDAP has been notified and is developing a fix expected in Hyrax 1.18.0 or later. CERT/CC recommends administrators review AllowedHosts configurations and restrict exposure of the gateway endpoint to trusted networks as an interim mitigation. There is no indication of active exploitation in the wild.
Mentioned in this report
Detection guidance
Hyrax/OLFS Server Process Initiating Outbound Connection to Internal RFC1918 Address
Detects the Java-based OPeNDAP Hyrax gateway (BES/OLFS running under Tomcat/Java) making outbound connections to private IP ranges, consistent with SSRF exploitation of the unvalidated redirect-following behaviour described in CVE-2026-16637. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Hyrax OPeNDAP Server Connecting to Internal RFC1918 Address
description: Detects the Hyrax OPeNDAP gateway process (OLFS/BES running under Java/Tomcat)
initiating outbound network connections to private/internal address space. Hyrax's
SSRF flaw allows attacker-supplied redirects to be followed without re-checking
AllowedHosts, causing the server itself to reach internal systems it should never
contact.
tags:
- attack.command-and-control
- attack.t1090
logsource:
category: network_connection
product: linux
detection:
selection:
Image|contains:
- java
CommandLine|contains:
- olfs
- opendap
- hyrax
internal_dest:
DestinationIp|startswith:
- '10.'
- 192.168.
- 172.16.
- 172.17.
- 172.18.
- 172.19.
- '172.2'
- 172.30.
- 172.31.
condition: selection and internal_dest
falsepositives:
- Legitimate Hyrax deployments configured to fetch datasets from internal storage/NAS
systems as part of normal operation
- Internal health-check or monitoring integrations that intentionally poll private-network
dataset sources
level: medium
id: 67630f3b-34b4-5065-83cb-3767fce272b2
status: experimental
author: Vorant
Legacy Earthdata Token Sent to Non-Earthdata Destination via Redirect
Detects the legacy Echo-Token/User-Id identifiers appearing in outbound HTTP requests to a destination host outside the expected Earthdata/NASA domain set, indicating the SSRF redirect-following flaw forwarded reusable credentials to an attacker-controlled host. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Legacy Echo-Token Header Leaked to External Host
description: Detects HTTP requests carrying the legacy Earthdata Echo-Token (or User-Id)
identifier destined for a host that is not part of the expected NASA/Earthdata domain
set. In the Hyrax SSRF flaw, these legacy identification headers are forwarded to
attacker-controlled redirect targets even though the primary Authorization token
is stripped, enabling session impersonation.
tags:
- attack.credential-access
- attack.t1552
logsource:
category: proxy
product: null
detection:
selection:
c-uri|contains:
- Echo-Token=
- echo_token=
- User-Id=
filter_earthdata:
DestinationHostname|endswith:
- .earthdata.nasa.gov
- .nasa.gov
condition: selection and not filter_earthdata
falsepositives:
- Internal proxies or CDN edge nodes fronting earthdata.nasa.gov that are not covered
by the domain suffix filter and need to be added to the allowlist
- Legitimate Earthdata federation partners that legally receive these legacy identifiers
under a documented data-sharing agreement
level: high
id: 83cc6415-f882-58d4-b92a-e4604793f272
status: experimental
author: Vorant
Hyrax Server Process Requesting Cloud Instance Metadata Endpoint
Detects the Hyrax OPeNDAP gateway process making an outbound request to the well-known cloud instance metadata address, a classic SSRF pivot target that the unvalidated redirect-follow behaviour would allow an attacker to reach for credential/token harvesting. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Hyrax Server Requesting Cloud Metadata Service Endpoint
description: Detects a Java/Tomcat process associated with the Hyrax OPeNDAP data
server (OLFS/BES) making an outbound connection to the standard cloud instance metadata
service address (169.254.169.254). Because Hyrax does not re-validate 3xx redirect
destinations against its AllowedHosts list, an SSRF exploit can redirect the server's
own outbound request to this address to harvest cloud credentials.
tags:
- attack.command-and-control
- attack.t1090
- attack.t1552
logsource:
category: network_connection
product: linux
detection:
selection:
Image|contains: java
CommandLine|contains:
- olfs
- opendap
- hyrax
DestinationIp: 169.254.169.254
condition: selection
falsepositives:
- Legitimate cloud-native monitoring or auto-configuration agents co-located with
the Hyrax process on the same host querying metadata for unrelated purposes
level: high
id: f699102a-3181-504b-b2d9-55c31207fc87
status: experimental
author: Vorant
Behavioural rules are generated from public reporting — validate in your environment before deploying.
Source reporting: https://kb.cert.org/vuls/id/305509
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