Hosted Maven mode edits only the root pom of a multi-module build, leaves child literals unpatched, and still attests VEX #261

[agent] Filed by Claude Code on behalf of Mikola Lysenko (@mikolalysenko) while adding Maven patch SBOM annotations to depscan. Repro artifacts were produced with real Maven and a stub patch API.

Summary

Vendored Maven refuses aggregator roots (vendor_maven_multimodule_unsupported). Hosted Maven does neither of the following:

• refuse the aggregator, or
• read the child poms.

When a module declares the patched GA with a literal base version, the rewriter can't find it in the root. It falls into the "transitive" branch and adds a root <dependencyManagement> pin. A child's literal <version> always beats an inherited depMgmt entry, so that module keeps resolving the unpatched upstream jar.

The scan reports redirected: 1, and socket-patch vex attests not_affected. VEX reads only the root pom, sees the suffixed depMgmt pin plus the repository, and trusts it.

Impact

• The module stays silently unpatched, which is fail-open.
• The VEX statement for the product is false.

Multi-module builds are the norm for non-trivial Maven projects.

Repro

Root pom.xml:

<project><modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId><artifactId>root</artifactId><version>1.0.0</version><packaging>pom</packaging>
  <modules><module>child</module></modules>
</project>

child/pom.xml: <parent>com.example:root:1.0.0</parent>, with a dependency on org.apache.commons:commons-lang3 <version>3.12.0</version>.

Grant: commons-lang3 3.12.0 → 3.12.0-socket.4d5e6f70, from the basic golden override.

socket-patch scan --mode hosted --json --yes ...
  -> exit 0, redirected=1, rewrittenFiles=[.mvn/checksums/checksums.sha256, .mvn/maven.config, pom.xml]
     warnings=[redirect_maven_dep_management_added]; child/pom.xml untouched
socket-patch vex --no-verify --product pkg:maven/com.example/[email protected]
  -> exit 0, not_affected for pkg:maven/org.apache.commons/[email protected]
mvn 3.9.6 -B dependency:3.6.1:copy-dependencies   (fresh local repo; Socket repo mirrored to a stub)
  -> Downloaded from central-https: .../commons-lang3/3.12.0/commons-lang3-3.12.0.jar
     BUILD SUCCESS; child/target/dependency/commons-lang3-3.12.0.jar is PRISTINE

Control: the child omits <version> and the root manages 3.12.0 in <dependencyManagement>. Here the root literal is rewritten, and the child resolves commons-lang3-3.12.0-socket.4d5e6f70.jar (PATCHED) from the Socket repo. So the gap is specific to module-level literals, and to modules that do not inherit from the root.

Expected vs actual

• Expected, one of:
  • (a) Refuse aggregator roots in hosted mode, like vendored mode does (<modules>, and Maven 4 <subprojects>).
  • (b) Walk the reactor (the <modules>/<subprojects> paths) and rewrite each module pom that declares the GA. This is what cargo hosted does for workspace members since Fix Cargo hosted workspace redirects #256.
  • At minimum: do not count a depMgmt-only pin as redirected when any module declares its own literal, and have VEX discovery refuse to attest a root pin that a module overrides.
• Actual: silent fail-open with a positive VEX.

CLI revision

3efdc31d

Suggested fix

Option (b) mirrors the cargo workspace-member handling. Option (a) is a one-line parity fix using declares_modules (plus subprojects). Either way, VEX discovery (vex/discover/maven.rs) should also look at module poms, or refuse when the root is an aggregator.

File refs (at 3efdc31)

• crates/socket-patch-cli/src/commands/scan/hosted.rs:70-81 (only root pom.xml / .mvn/* are read)
• crates/socket-patch-core/src/patch/redirect/mod.rs:6143-6170 (a GA absent from the root becomes a depMgmt pin)
• crates/socket-patch-core/src/vendor/maven_repo.rs:242,1109 (the vendored-side refusal hosted lacks)