CVE-2021-3838 | PHAR Deserialization in dompdf/dompdf

Exp

DomPDF before version 2.0.0 is vulnerable to PHAR deserialization due to a lack of checking on the protocol before passing it into the file_get_contents() function. An attacker who can upload files of any type to the server can pass in the phar:// protocol to unserialize the uploaded file and instantiate arbitrary PHP objects. This can lead to remote code execution, especially when DOMPdf is used with frameworks with documented POP chains like Laravel or vulnerable developer code.

Published: 2024-11-15 Last update: 2024-11-19 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3838 is rated High Exploit Risk (85.7/100): CVSS Critical severity, with high exploitation likelihood (EPSS 6.93%, 92th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-3838

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-3838

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-29 7.47% 6.93% -0.54%
2 2026-05-28 4.88% 7.47% +2.59%
3 2026-04-06 — 4.88% —

Full EPSS history (20 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3838

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0
9.8 3.0 CRITICAL
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]

Weakness enumeration for CVE-2021-3838

GitHub Security Advisory for CVE-2021-3838

GHSA-577p-7j7h-2jgf · Severity: critical · Ecosystem: composer — Deserialization of Untrusted Data in dompdf/dompdf

OS Trackers for CVE-2021-3838

vendor priority summary link
debian not yet assigned CVE-2021-3838 not yet assigned priority: Debian including 1 source packages (php-dompdf), 3 status rows across 3 suites (bookworm, bullseye, sid): resolved 3. https://security-tracker.debian.org/tracker/CVE-2021-3838
ubuntu medium CVE-2021-3838 medium priority: Ubuntu including 1 source packages (php-dompdf), 8 status rows across 8 suites (bionic, focal, jammy, kinetic, lunar, trusty, upstream, xenial): released 5, ignored 2, DNE 1. https://ubuntu.com/security/CVE-2021-3838

Affected software / configurations for CVE-2021-3838

Vendor Product Version Raw CPE
dompdf_project dompdf < 2.0.0 cpe:2.3:a:dompdf_project:dompdf:*:*:*:*:*:*:*:*

References for CVE-2021-3838

cvelogic Threat Intelligence