Security Digest · Vulnerability record
CVE-2021-3902: Improper Restriction of XML External Entity Reference in dompdf/dompdf
An improper restriction of external entities (XXE) vulnerability in dompdf/dompdf's SVG parser allows for Server-Side Request Forgery (SSRF) and deserialization attacks.
CVSS 9.8 Critical EPSS 1.0% · p61
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.0%, percentile 61: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 61% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
dompdf/dompdf(Composer (PHP)) < 2.0.0, fixed in 2.0.0. Check your lockfile, including transitive dependencies.
What it is
An improper restriction of external entities (XXE) vulnerability in dompdf/dompdf's SVG parser allows for Server-Side Request Forgery (SSRF) and deserialization attacks. This issue affects all versions prior to 2.0.0. The vulnerability can be exploited even if the isRemoteEnabled option is set to false. It allows attackers to perform SSRF, disclose internal image files, and cause PHAR deserialization attacks.
From the GitHub advisory
An improper restriction of external entities (XXE) vulnerability in dompdf/dompdf's SVG parser allows for Server-Side Request Forgery (SSRF) and deserialization attacks. This issue affects all versions prior to 2.0.0. The vulnerability can be exploited even if the isRemoteEnabled option is set to false. It allows attackers to perform SSRF, disclose internal image files, and cause PHAR deserialization attacks.
Weakness type: CWE-611.
Product: dompdf/dompdf (Composer (PHP)) · Assigned by: @huntr_ai · Published: 2024-11-15
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| Composer (PHP) | dompdf/dompdf | < 2.0.0 | 2.0.0 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| dompdf | dompdf/dompdf | unspecified < 2.0.0 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| @huntr_ai | 3.0 | 9.8 Critical | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| CISA-ADP | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| GitHub | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.95% probability of exploitation activity in the next 30 days; percentile 61.
Timeline
- — CVE record published by @huntr_ai
- — GitHub-reviewed advisory GHSA-3vjh-xrhf-v9xh published (critical)
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-3vjh-xrhf-v9xh github.com
- CVE.org record CVE-2021-3902 cve.org
- NVD entry CVE-2021-3902 nvd.nist.gov
Other references from the CVE record and advisory
- huntr.com huntr.com
- github.com github.com
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