Security readout for executives and security teams
Plain-English summary
Puppet Agent had a module that could deserialize untrusted user-supplied data. That kind of flaw can allow serious compromise if reachable by an attacker, but the published CVSS requires high privileges and high complexity. Puppet says the issue is resolved in Puppet Agent 7.4.0.
Executive priority
Schedule remediation in the normal vulnerability cycle, with higher priority for systems that administer infrastructure or hold privileged automation credentials. The issue has serious potential impact, but current sources do not show active exploitation and require high attacker privilege.
Technical view
CVE-2021-27017 is CWE-502 in Puppet Agent. The CVSS 3.1 vector is AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H, indicating potential high confidentiality, integrity, and availability impact, but only after high-privilege access and difficult exploitation conditions. The source bundle does not identify the specific module or affected version range.
Likely exposure
Exposure is most relevant to environments running Puppet Agent versions that have not incorporated the 7.4.0 fix. The bundle does not provide a precise affected version range, so asset validation should compare deployed agent versions against Puppet's advisory and local package inventories.
Exploitation context
The bundle marks KEV as false and provides no cited evidence of active exploitation. The CVSS vector suggests network reachability, but exploitation is constrained by high privileges and high attack complexity. Treat this as important for managed infrastructure, not as confirmed mass exploitation.
Researcher notes
The public bundle is sparse: it names deserialization of untrusted data, Puppet Agent, CWE-502, and the 7.4.0 resolution. It does not describe the vulnerable module, exploit preconditions beyond CVSS, affected version boundaries, or operational mitigations beyond upgrading/checking vendor guidance.
Mitigation direction
- Upgrade Puppet Agent to 7.4.0 or later per Puppet guidance.
- Review Puppet's CVE page for environment-specific upgrade notes.
- Prioritize Puppet agents on management servers and privileged automation hosts.
- Restrict access to Puppet management interfaces and agent administration paths.
- Track remediation through configuration management inventory.
Validation and detection
- Inventory Puppet Agent versions across servers and workstations.
- Flag agents older than the fixed 7.4.0 release for review.
- Confirm package manager or deployment records show the upgraded agent.
- Check vulnerability scanner findings against Puppet's advisory.
- Document any exceptions where upgrade is deferred.
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.
CWE-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-27017 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
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:H/UI:N/S:U/C:H/I:H/A:H0.75.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.6MediumVector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Source materials
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.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.