Security readout for executives and security teams
Plain-English summary
A malicious InDesign file could corrupt application memory and run attacker-controlled code with the victim’s user permissions. An attacker must persuade a user to open the file, but successful exploitation could expose data, alter files, or disrupt the workstation.
Executive priority
Prioritize remediation for systems whose users routinely exchange external design files. The required user interaction reduces immediacy compared with network-exploitable flaws, but potential confidentiality, integrity, and availability impact is high. Escalate promptly where exposed users hold elevated privileges or access sensitive information.
Technical view
CVE-2026-21304 is a heap-based buffer overflow (CWE-122) in Adobe InDesign Desktop. It has CVSS 3.1 score 7.8 and vector AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. The supplied description identifies versions 21.0, 19.5.5, and earlier, although the structured affected-version data is inconsistent.
Likely exposure
Exposure is concentrated on endpoints running the identified InDesign versions, particularly where users receive or download files from untrusted sources. Exploitation is local and requires a victim to open a malicious file; it does not indicate unauthenticated remote compromise.
Exploitation context
The source bundle says exploitation requires user interaction and executes code in the current user’s context. The CVE is not listed as a CISA KEV in the supplied data, and no cited source establishes active exploitation. Absence from KEV does not prove exploitation has never occurred.
Researcher notes
The weakness is CWE-122 with low attack complexity, no required privileges, and required user interaction. Scope remains unchanged, while confidentiality, integrity, and availability impacts are each rated high. Confirm version boundaries directly with Adobe because the supplied structured version array conflicts with the narrative description.
Mitigation direction
- Review Adobe advisory APSB26-02 for authoritative affected-version and remediation guidance.
- Apply the Adobe-supported remediation identified by the advisory across affected endpoints.
- Warn users not to open unexpected or untrusted InDesign-compatible files.
- Limit user privileges where operationally practical to reduce post-exploitation impact.
Validation and detection
- Inventory installed InDesign versions and compare them with Adobe APSB26-02.
- Confirm the vendor-prescribed remediation is installed on every affected endpoint.
- Verify software-management reports show no remaining vulnerable installations.
- Review security telemetry for suspicious files opened by InDesign and unexpected child processes.
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-122: 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 lookupExecution 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-2026-21304 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
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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.
SSVC decision data
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:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H1.85.9adobeVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/indesign/apsb26-02.htmlCVE reference, adobe · vendor-advisory
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.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.