CVE-2020-21896Public exploit

Application crash via stale pointer after reallocation

Published Aug 22, 2023 · Updated Nov 3, 2025

Use-after-free in MuPDF 1.16.0 allows context-dependent attackers to crash the application by inducing processing of a crafted PDF. In svg_dev_text_span_as_paths_defs, fz_run_t3_glyph can recurse and reallocate sdev->fonts, leaving fnt pointing to freed storage until the code dereferences it. Exploitation requires a crafted PDF to be opened or otherwise processed; the documented consequence is an application crash, not code execution or data access.

CVSS severity5.5
Medium
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Use-after-free in MuPDF 1.16.0 allows context-dependent attackers to crash the application by inducing processing of a crafted PDF. In svg_dev_text_span_as_paths_defs, fz_run_t3_glyph can recurse and reallocate sdev->fonts, leaving fnt pointing to freed storage until the code dereferences it. Exploitation requires a crafted PDF to be opened or otherwise processed; the documented consequence is an application crash, not code execution or data access.

The record

CVE
CVE-2020-21896
Published
Aug 22, 2023
Updated
Nov 3, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 22, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1204.002Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo