VulnerabilityPublished 28 Oct 2026

CVE-2026-58273: rucio has an Authorization Bypass on REST API endpoint for signing URLs

Affects rucioSource GCVE Database

Not known to be exploited · CVSS 8.8 High : upgrade to 35.9.0 soon.

Data as of 28 Oct 2026, 21:14 UTC

CVSS 3.1 base score

8.8High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 35.9.0, 38.6.0, 41.0.0rc1

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade rucio to 35.9.0; rucio to 38.6.0; rucio to 41.0.0rc1.

Affected software

Product	Affected	Fixed in
PyPIrucio	Affected >=1.16.1 <35.9.0	Fixed in 35.9.0
PyPIrucio	Affected >=36.0.0rc1 <38.6.0	Fixed in 38.6.0
PyPIrucio	Affected >=39.0.0rc1 <41.0.0rc1	Fixed in 41.0.0rc1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Summary The `/credentials/signurl` endpoint decides authorization from the client-supplied `X-Rucio-Account` HTTP header instead of the authenticated token's account. Any client holding **any** valid auth token (even a low-privilege account they legitimately own) can send `X-Rucio-Account: root` to pass the root-only permission check and have the Rucio server mint a presigned **read / write / delete** URL for an **arbitrary** object, signed with the RSE's stored S3 / GCS / Swift credentials. ## Details `SignURL.get()` takes the authorization principal from a request header and never uses the token-authenticated identity: ```python # lib/rucio/web/rest/flaskapi/v1/credentials.py account = request.headers.get('X-Rucio-Account', default=None) # L165 (attacker-controlled) ... result = get_signed_url(account, rse=rse, service=service, # L194 operation=operation, url=url, lifetime=lifetime, vo=vo) ``` The gateway then uses that header value as the `issuer` for the permission check: ```python # lib/rucio/gateway/credential.py auth_result = permission.has_permission(issuer=account, vo=vo, # L57 action='get_signed_url', kwargs=kwargs, ...) ``` and the permission function is root-only: ```python # lib/rucio/core/permission/generic.py def perm_get_signed_url(issuer, kwargs, session): return _is_root(issuer) # _is_root(x) -> x.external == 'root' ``` `InternalAccount('root', vo).external == 'root'` unconditionally, so the gate passes whenever the header is `root`. The endpoint is on `AuthenticatedBlueprint`, whose `before_request` hook validates the token and sets `request.environ['issuer']` **from the token** — but nothing ever compares `X-Rucio-Account` to it: ```python # lib/rucio/web/rest/flaskapi/v1/common.py (request_auth_env) flask.request.environ['issuer'] = auth.get('account') # L168 (the real account; unused by SignURL) ``` This is anomalous: every other authenticated handler derives the account from `request.environ['issuer']`; `credentials.py` is the only one that trusts the header. Additionally, `core.credential.get_signed_url` never checks that the supplied `url`'s host/bucket belongs to the target RSE, so even a legitimate `root` caller gets an arbitrary-object signing oracle. In multi-VO the VO is also read from the `X-Rucio-VO` header, allowing cross-tenant targeting. ## Proof of concept Request (any valid token + spoofed account): ``` GET /credentials/signurl?rse=<cloudRSE>&svc=s3&op=delete&url=https://victim-bucket.s3.amazonaws.com/important/dataset.root HTTP/1.1 X-Rucio-Auth-Token: <any valid token, even a low-privilege account> X-Rucio-Account: root Accept: application/octet-stream ``` Response: `200 OK` with a presigned DELETE URL the attacker replays directly against the storage backend. ## Impact A low-privilege Rucio user can read, overwrite, and delete arbitrary objects on any cloud-backed (S3/GCS/Swift) RSE using the server's stored credentials — enabling data exfiltration, tampering, and destruction, and cross-tenant access in multi-VO deployments. ## Credit Reported by seankohjs. Found via static analysis + manual verification.

CWE-639Authorization Bypass Through User-Controlled Key (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #24OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Architecture and Design
For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
Architecture and Design · Implementation
Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
Architecture and Design
Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.1.2 (opens in a new tab)
V4.2.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-639

Technical details

References

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