CVE-2020-36430

Service interruption via undersized font decode buffer

Published Jul 20, 2021 · Updated Aug 4, 2024

Heap-based buffer overflow in libass 0.15.x before 0.15.1 allows context-dependent attackers to crash applications via crafted ASS data. The decode_font allocation computes decoded size with unsigned subtraction inside FFMAX, so a zero remainder wraps and allocates one byte too little before decode_chars writes. Exploitation requires control of an ASS track consumed by a libass-based application, and the documented consequence is an assertion failure and service interruption.

CVSS severity7.8
High
EPSS probability1.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in libass 0.15.x before 0.15.1 allows context-dependent attackers to crash applications via crafted ASS data. The decode_font allocation computes decoded size with unsigned subtraction inside FFMAX, so a zero remainder wraps and allocates one byte too little before decode_chars writes. Exploitation requires control of an ASS track consumed by a libass-based application, and the documented consequence is an assertion failure and service interruption.

The record

CVE
CVE-2020-36430
Published
Jul 20, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1204.002
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Jul 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

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.

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No observations available

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

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1204.002Malicious File

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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