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9.9
Parse Server allows attackers to steal user session tokens
CVE-2026-30965
GHSA-6r2j-cxgf-495f
Summary
An attacker can steal session tokens from other users by exploiting a vulnerability in Parse Server's query handling. This can be done by creating or updating an object with a new relation field, allowing the attacker to take over user accounts. To protect against this, update to the latest version of Parse Server or restrict Class-Level Permissions to prevent clients from creating new fields on classes.
What to do
- Update parse-server to version 9.5.2-alpha.8.
- Update parse-server to version 8.6.21.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| – | parse-server | > 9.0.0-alpha.1 , <= 9.5.2-alpha.8 | 9.5.2-alpha.8 |
| – | parse-server | <= 8.6.21 | 8.6.21 |
| parseplatform | parse-server | <= 8.6.21 | – |
| parseplatform | parse-server | > 9.0.0 , <= 9.5.2 | – |
| parseplatform | parse-server | 9.5.2 | – |
| parseplatform | parse-server | 9.5.2 | – |
| parseplatform | parse-server | 9.5.2 | – |
| parseplatform | parse-server | 9.5.2 | – |
| parseplatform | parse-server | 9.5.2 | – |
| parseplatform | parse-server | 9.5.2 | – |
| parseplatform | parse-server | 9.5.2 | – |
Original title
Parse Server vulnerable to session token exfiltration via `redirectClassNameForKey` query parameter
Original description
### Impact
A vulnerability in Parse Server's query handling allows an authenticated or unauthenticated attacker to exfiltrate session tokens of other users by exploiting the `redirectClassNameForKey` query parameter. Exfiltrated session tokens can be used to take over user accounts.
The vulnerability requires the attacker to be able to create or update an object with a new relation field, which depends on the Class-Level Permissions of at least one class.
### Patches
The fix applies the same security checks that normally protect class access after the query redirect, ensuring that queries redirected via `redirectClassNameForKey` are subject to the same restrictions as direct queries to the target class.
### Workarounds
Set restrictive Class-Level Permissions to prevent clients from creating new fields on classes, specifically by disabling `addField` for public access and unauthenticated users. Note that this limits client functionality and does not fully eliminate the risk if a relation field pointing to a protected class already exists in the schema.
### References
- GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-6r2j-cxgf-495f
- Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.5.2-alpha.8
- Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.21
A vulnerability in Parse Server's query handling allows an authenticated or unauthenticated attacker to exfiltrate session tokens of other users by exploiting the `redirectClassNameForKey` query parameter. Exfiltrated session tokens can be used to take over user accounts.
The vulnerability requires the attacker to be able to create or update an object with a new relation field, which depends on the Class-Level Permissions of at least one class.
### Patches
The fix applies the same security checks that normally protect class access after the query redirect, ensuring that queries redirected via `redirectClassNameForKey` are subject to the same restrictions as direct queries to the target class.
### Workarounds
Set restrictive Class-Level Permissions to prevent clients from creating new fields on classes, specifically by disabling `addField` for public access and unauthenticated users. Note that this limits client functionality and does not fully eliminate the risk if a relation field pointing to a protected class already exists in the schema.
### References
- GitHub security advisory: https://github.com/parse-community/parse-server/security/advisories/GHSA-6r2j-cxgf-495f
- Fix Parse Server 9: https://github.com/parse-community/parse-server/releases/tag/9.5.2-alpha.8
- Fix Parse Server 8: https://github.com/parse-community/parse-server/releases/tag/8.6.21
nvd CVSS4.0
9.9
Vulnerability type
CWE-863
Incorrect Authorization
- https://github.com/parse-community/parse-server/releases/tag/8.6.21
- https://github.com/parse-community/parse-server/releases/tag/9.5.2-alpha.8
- https://github.com/parse-community/parse-server/security/advisories/GHSA-6r2j-cx...
- https://nvd.nist.gov/vuln/detail/CVE-2026-30965
- https://github.com/advisories/GHSA-6r2j-cxgf-495f
Published: 11 Mar 2026 · Updated: 13 Mar 2026 · First seen: 10 Mar 2026