# SA-2026-032: Drain passphrases derive from a key the server also sees

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Security advisory SA-2026-032 (low, open): Drain passphrases derive from a key the server also sees.

[Advisories](../index.html) / SA-2026-032

# SA-2026-032: Drain passphrases derive from a key the server also sees

Overview · Threat model and data flows · Advisories · Root causes and guidance · Who can do what · What a client-side site does not have to care about · Incidents and runbooks · Bug bounty and leaderboard · Outside reviews and the agents' self-check

|  |  |
|---|---|
| **Severity** | low |
| **Status** | open |
| **Weakness** | CWE-321 |
| **Component** | `admin/build/postmaster.py` |
| **Found by** | security@php.newsroom (pass 2 review) |
| **Found** | 2026-10-24 |
| **Fixed in** | not yet |

## What it is

The lane key pair's passphrase and enum key are derived from the vault's write key, which is also sent to the vault server, and the endpoint comes from a file in the vault.

## What an attacker could do

The server, or anyone logging its headers, holds the passphrase.

**How:** Public in outline.

## Root cause

Deriving from the nearest key rather than from the client-only secret.

## What was not in place

Derive from the part of the key that never leaves the client.

## What would fix it

Derive from the vault key's secret part; pin the endpoint.


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site v0.18.0 · data as of 2026-10-24T16:05Z · vault commit 8c16a64a7cf6 · https://php.oct.2026.newsroom.sgit.ai/admin/appsec/advisories/SA-2026-032/index.html