Security readout for executives and security teams
Plain-English summary
dompdf is a PHP library used to generate PDFs. This CVE lets malicious SVG content trigger XML external entity handling in dompdf before 2.0.0, creating risk of internal network requests, local image disclosure, and PHP PHAR deserialization. The high score reflects remote, unauthenticated impact when applications process attacker-controlled content.
Executive priority
Treat this as urgent for any service generating PDFs from external input. The business risk is data exposure or internal service access through a document-rendering feature that may look low risk operationally.
Technical view
CVE-2021-3902 is a CWE-611 XXE flaw in dompdf/dompdf's SVG parser. Sources state all versions before 2.0.0 are affected, and exploitation can work even when isRemoteEnabled is false. Reported impacts include SSRF, internal image file disclosure, and PHAR deserialization attacks.
Likely exposure
Exposure is most likely in PHP applications using dompdf/dompdf before 2.0.0 to render PDFs from user-controlled HTML or SVG. Systems that only process trusted static templates have lower practical exposure, but still need version validation.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. The vulnerability is still high urgency because it is remote, unauthenticated, low-complexity, and affects common PDF-generation workflows involving attacker-controlled content.
Researcher notes
Key validation is dependency version plus data-flow review. The important nuance is that isRemoteEnabled=false is not a complete control for this issue, according to the source description. Avoid assuming exploit activity without separate evidence.
Mitigation direction
- Inventory applications and dependencies using dompdf/dompdf.
- Upgrade dompdf/dompdf to version 2.0.0 or later.
- Do not rely on isRemoteEnabled=false as a protection.
- If upgrade is delayed, check dompdf guidance and limit untrusted SVG rendering.
- Prioritize internet-facing PDF generation paths first.
Validation and detection
- Check composer.json and composer.lock for dompdf/dompdf versions below 2.0.0.
- Identify routes or jobs that generate PDFs from user-supplied HTML or SVG.
- Confirm deployed builds use the upgraded dompdf package.
- Review PDF-generation logs for unusual internal-resource access patterns.
- Add regression tests covering untrusted SVG handling where applicable.
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-611: 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 lookupCloud metadata behavior lookup
The CVE wording references SSRF or metadata access, so cloud discovery and credential material review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-3902 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
- Critical
- CVSS
- 9.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/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:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
9.8CriticalVector: CVSS:3.0/AV:N/AC:L/PR:N/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.
Improper Restriction of XML External Entity Reference
Improper Restriction of XML External Entity Reference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.