CVE-2021-36978

MEDIUMNVD 5.55.5—

5.5

QPDF 9.x through 9.1.1 and 10.x through 10.0.4 has a heap-based buffer overflow in Pl_ASCII85Decoder::write (called from Pl_AES_PDF::flush and Pl_AES_PDF::finish) when a certain downstream write fails.

CVSS v3: 5.5
EG Score: 5.5(medium)
EPSS: 23.4%
KEV: Not listed

Published

July 20, 2021

Last Modified

November 21, 2024

References (12)

cve@mitrehttps://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28262
cve@mitrehttps://github.com/google/oss-fuzz-vulns/blob/main/vulns/qpdf/OSV-2020-2245.yaml
cve@mitrehttps://github.com/qpdf/qpdf/commit/dc92574c10f3e2516ec6445b88c5d584f40df4e5
cve@mitrehttps://github.com/qpdf/qpdf/issues/492
cve@mitrehttps://lists.debian.org/debian-lts-announce/2023/08/msg00037.html
cve@mitrehttps://security.gentoo.org/glsa/202401-20
af854a3a-2127-422b-91ae-364da2661108https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28262
af854a3a-2127-422b-91ae-364da2661108https://github.com/google/oss-fuzz-vulns/blob/main/vulns/qpdf/OSV-2020-2245.yaml
af854a3a-2127-422b-91ae-364da2661108https://github.com/qpdf/qpdf/commit/dc92574c10f3e2516ec6445b88c5d584f40df4e5
af854a3a-2127-422b-91ae-364da2661108https://github.com/qpdf/qpdf/issues/492
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2023/08/msg00037.html
af854a3a-2127-422b-91ae-364da2661108https://security.gentoo.org/glsa/202401-20

Patch Availability(2)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	libqpdf26 (9.1.1-1ubuntu0.1) @ focal	2026-05-26	ubuntu
ubuntu	qpdf (8.0.2-3~16.04.1+esm1) @ xenial	2026-05-26	ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-787Out-of-bounds Write

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 12× in last 7d / 20× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

2026-06-08 14:15 UTCEPSS rescore
2026-06-08 14:15 UTCEPSS rescore
2026-06-07 15:23 UTCEPSS rescore
2026-06-07 15:23 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-06 13:46 UTCEPSS rescore
2026-06-05 22:45 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-05 06:09 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-04 13:10 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-02 20:11 UTCEPSS rescore
2026-06-01 13:50 UTCEPSS rescore
2026-06-01 13:50 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 22:29 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore
2026-05-31 00:15 UTCEPSS rescore

Frequently asked(5)

What is CVE-2021-36978?

CVE-2021-36978 is a medium vulnerability published on July 20, 2021. QPDF 9.x through 9.1.1 and 10.x through 10.0.4 has a heap-based buffer overflow in PlASCII85Decoder::write (called from PlAESPDF::flush and PlAES_PDF::finish) when a certain downstream write fails.

When was CVE-2021-36978 disclosed?

CVE-2021-36978 was first published in the National Vulnerability Database on July 20, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-36978 actively exploited?

CVE-2021-36978 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 23.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-36978?

CVE-2021-36978 has a CVSS v3 base score of 5.5 (NVD).

How do I remediate CVE-2021-36978?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-36978, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-36978

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