CVE-2021-36978Public exploit

Application crash via stale ASCII85 decoder state

Published Jul 20, 2021 · Updated Oct 15, 2024

Heap-based buffer overflow in QPDF 9.0.0 through 9.1.1 and 10.0.0 through 10.0.4 allows local users to crash QPDF. The Pl_ASCII85Decoder pipeline calls a downstream write before resetting its position and input buffer, so an exception leaves stale decoder state that a later write reuses beyond valid heap storage. When a user processes a crafted PDF that makes the downstream pipeline throw, the process aborts and interrupts that QPDF operation.

CVSS severity5.5
Medium
EPSS probability1.27%
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 QPDF 9.0.0 through 9.1.1 and 10.0.0 through 10.0.4 allows local users to crash QPDF. The Pl_ASCII85Decoder pipeline calls a downstream write before resetting its position and input buffer, so an exception leaves stale decoder state that a later write reuses beyond valid heap storage. When a user processes a crafted PDF that makes the downstream pipeline throw, the process aborts and interrupts that QPDF operation.

The record

CVE
CVE-2021-36978
Published
Jul 20, 2021
Updated
Oct 15, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 15, 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 vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5SUSECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
7.8Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/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-787Out-of-bounds Write
T1499.004Application or System Exploitation

Public exploit references

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

Technologies

Your stack

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Your stack

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