Security readout for executives and security teams
Plain-English summary
CVE-2021-39228 is a memory safety flaw in Tremor. Under a specific Tremor script pattern, the system can keep references to freed memory, and later expose that memory when state is retrieved or sent externally. Business risk is mainly unintended data disclosure or corrupted processing, not service outage.
Executive priority
Treat as a moderate-priority remediation for environments using Tremor in data pipelines or external event processing. Prioritize systems that emit state over network channels, because the stated impact includes access to memory regions that may have been freed.
Technical view
Affected Tremor versions greater than 0.7.2 and before 0.11.6 can create use-after-free or expired-reference behavior when patch or merge is applied to state and immediately assigned back to state. The issue was fixed in 0.11.6 by always cloning the merge or patch target expression.
Likely exposure
Exposure is limited to Tremor servers, or programs using tremor-script, that execute scripts containing the affected state reassignment pattern. Organizations not using Tremor or tremor-script are not exposed based on the provided sources.
Exploitation context
The source bundle does not identify active exploitation, and KEV status is false. The vulnerability requires the affected script construct to execute, after which state retrieval, such as via TCP or HTTP output, may access memory that should no longer be referenced.
Researcher notes
The vulnerability maps to CWE-416 and CWE-825, with CVSS 3.1 score 6.5. The fix removes an optimization rather than adding a runtime guard. Evidence supports affected version range, root condition, and remediation, but not real-world exploitation prevalence.
Mitigation direction
- Upgrade Tremor or tremor-script dependencies to version 0.11.6 or later.
- If upgrading is blocked, avoid immediately reassigning patch or merge results back to state.
- Use a temporary variable workaround as described by the vendor advisory.
- Check vendor guidance before applying any broader operational workaround.
Validation and detection
- Inventory Tremor runtime and tremor-script versions across deployed services.
- Review Tremor scripts for patch or merge applied to state with immediate reassignment.
- Confirm affected services run version 0.11.6 or later.
- Verify any temporary-variable workaround is documented and covered by tests.
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-416: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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 lookupCWE-825: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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-2021-39228 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
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
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:L/PR:N/UI:N/S:U/C:L/I:L/A:N3.92.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/tremor-rs/tremor-runtime/security/advisories/GHSA-mc22-5q92-8v85CVE reference · x_refsource_CONFIRM
- https://github.com/tremor-rs/tremor-runtime/pull/1217CVE reference · x_refsource_MISC
- https://github.com/tremor-rs/tremor-runtime/commit/1a2efcdbe68e5e7fd0a05836ac32d2cde78a0b2eCVE reference · x_refsource_MISC
- https://github.com/tremor-rs/tremor-runtime/releases/tag/v0.11.6CVE 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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Expired Pointer Dereference
Expired Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.