Security readout for executives and security teams
Plain-English summary
CVE-2021-23406 is a high-severity remote code execution issue in pac-resolver before 5.0.0. The risk appears when software processes PAC proxy files from untrusted input. A successful attack could affect confidentiality, integrity, and availability. The provided sources do not show CISA KEV listing or confirmed active exploitation.
Executive priority
Treat this as a high-priority dependency remediation when pac-resolver is present and PAC files can be influenced externally. Prioritize internet-facing, multi-tenant, proxy, or automation systems first. If only trusted static PAC files are used, urgency is lower but upgrade should still be scheduled.
Technical view
pac-resolver before 5.0.0 handled PAC files unsafely when given untrusted input. The published note says the fix was applied in node-degenerator, a dependency maintained by the same maintainer. CVSS 3.1 is 8.1 with network attack vector, no privileges, no user interaction, high impact, and high attack complexity.
Likely exposure
Exposure is most likely in Node.js dependency trees that include pac-resolver before 5.0.0 and evaluate PAC content influenced by users, networks, tenants, or other untrusted sources. The Java WebJars Snyk advisory suggests packaged dependency exposure may also matter. Static, trusted PAC configuration reduces practical risk.
Exploitation context
The source bundle does not establish active exploitation; KEV is false. The CVSS vector indicates network reachability, no required privileges, no user interaction, and high attack complexity. Exploitation depends on unsafe handling of untrusted PAC input, so validation should focus on whether the vulnerable code path is reachable.
Researcher notes
Key uncertainty is reachability: the advisory requires untrusted input. Confirm the exact pac-resolver version and resolved node-degenerator dependency. The fix is documented as landing in node-degenerator, so dependency override behavior matters. Do not assume exploitation in the environment without PAC input control evidence.
Mitigation direction
- Upgrade pac-resolver to version 5.0.0 or later.
- Ensure node-degenerator resolves to a version containing the referenced fixes.
- Audit direct and transitive dependency lockfiles for vulnerable pac-resolver versions.
- Avoid evaluating PAC files or PAC content from untrusted sources.
- Check vendor or package advisory guidance before deploying compensating controls.
Validation and detection
- Inventory package manifests and lockfiles for pac-resolver below 5.0.0.
- Check SCA results for JavaScript and WebJars dependency paths.
- Review code paths that load or evaluate PAC content.
- Confirm PAC input sources are trusted, authenticated, and controlled.
- Verify deployed builds use the fixed dependency resolution.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
Execution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-23406 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P2.25.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P
Source materials
- CVE List V5 sourceCVE List V5
- https://snyk.io/vuln/SNYK-JS-PACRESOLVER-1564857CVE reference · x_refsource_MISC
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1568506CVE reference · x_refsource_MISC
- https://github.com/TooTallNate/node-degenerator/commit/ccc3445354135398b6eb1a04c7d27c13b833f2d5CVE reference · x_refsource_MISC
- https://github.com/TooTallNate/node-degenerator/commit/9d25bb67d957bc2e5425fea7bf7a58b3fc64ff9eCVE reference · x_refsource_MISC
- https://github.com/TooTallNate/node-pac-resolver/releases/tag/5.0.0CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.