PostgresNIO processes unencrypted bytes from man-in-the-middle (GHSA-9cfh-vx93-84vv)
Aliases: CVE-2023-31136
Published: 2023-05-10T19:20:16Z
Severity: type: CVSS_V3
score: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Affected: [{'package': {'ecosystem': 'purl-type:swift', 'name': 'github.com/vapor/postgres-nio'}, 'ranges': [{'type': 'ECOSYSTEM', 'events': [{'introduced': '0'}, {'fixed': '1.14.2'}]}]}]

### Impact
Any user of PostgresNIO connecting to servers with TLS enabled is vulnerable to a man-in-the-middle attacker injecting false responses to the client's first few queries, despite the use of TLS certificate verification and encryption.

_The remaining text in this section is quoted verbatim from [PostgreSQL's CVE-2021-23222 advisory](https://www.postgresql.org/support/security/CVE-2021-23222/):_

> If more preconditions hold, the attacker can exfiltrate the client's password or other confidential data that might be transmitted early in a session. The attacker must have a way to trick the client's intended server into making the confidential data accessible to the attacker. A known implementation having that property is a PostgreSQL configuration vulnerable to [CVE-2021-23214](https://www.postgresql.org/support/security/CVE-2021-23214/). As with any exploitation of [CVE-2021-23214](https://www.postgresql.org/support/security/CVE-2021-23214/), the server must be using trust authentication with a clientcert requirement or using cert authentication. To disclose a password, the client must be in possession of a password, which is atypical when using an authentication configuration vulnerable to [CVE-2021-23214](https://www.postgresql.org/support/security/CVE-2021-23214/). The attacker must have some other way to access the server to retrieve the exfiltrated data (a valid, unprivileged login account would be sufficient).

### Patches
The vulnerability is addressed in PostgresNIO versions starting from [1.14.2](https://github.com/vapor/postgres-nio/releases/tag/1.14.2) via [2df54bc94607f44584ae6ffa74e3cd754fffafc7](https://github.com/vapor/postgres-nio/commit/2df54bc94607f44584ae6ffa74e3cd754fffafc7), which required [additional support](https://github.com/apple/swift-nio/pull/2419) from SwiftNIO.

### Workarounds
There are no known workarounds for unpatched users.

### Additional Credits
Special thanks to PostgreSQL's Tom Lane <[tgl@sss.pgh.pa.us](mailto:tgl@sss.pgh.pa.us)> for reporting this issue!

### References
- [PostgreSQL security advisory for CVE-2021-23222](https://www.postgresql.org/support/security/CVE-2021-23222/)
- [GitHub security advisory GHSA-735f-7qx4-jqq5 for CVE-2021-23222](https://github.com/advisories/GHSA-735f-7qx4-jqq5)
- [PostgreSQL security advisory for CVE-2021-23214](https://www.postgresql.org/support/security/CVE-2021-23214/)
- [GitHub security advisory GHSA-467w-rrqc-395f for CVE-2021-23214](https://github.com/advisories/GHSA-467w-rrqc-395f)
- [SwiftNIO PR #2419 Add unprocessedBytes property on NIOSingleStepByteToMessageProcessor](https://github.com/apple/swift-nio/pull/2419)
- [PostgresNIO commit 2df54bc94607f44584ae6ffa74e3cd754fffafc7](https://github.com/vapor/postgres-nio/commit/2df54bc94607f44584ae6ffa74e3cd754fffafc7)
- [PostgresNIO 1.42.2 release](https://github.com/vapor/postgres-nio/releases/tag/1.14.2)