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Fencer Vulns
medium 5.5

CVE-2021-37220 json

MuPDF through 1.18.1 has an out-of-bounds write because the cached color converter does not properly consider the maximum key size of a has…

published 2021-07-21 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-23792

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

MuPDF through 1.18.1 has an out-of-bounds write because the cached color converter does not properly consider the maximum key size of a hash table. This can, for example, be seen with crafted "mutool draw" input.

Patch / fix

  • mupdf Debian 14, Debian 13, Debian 12 1.17.0+ds1-2

debian advisories DEBIAN-CVE-2021-37220

  • mupdf Ubuntu Pro 18.04 LTS 1.12.0+ds1-1ubuntu0.1~esm1
  • mupdf Ubuntu Pro 20.04 LTS 1.16.1+ds1-1ubuntu1+esm1

ubuntu advisories UBUNTU-CVE-2021-37220

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • mupdf Arch Linux 1.19.0-1

arch linux advisories AVG-2205

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-37220 updated cvss 4.8

mupdf: out-of-bounds write because the cached color converter does not properly consider the maximum key size of a hash table

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.33% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugs.ghostscript.com https://bugs.ghostscript.com/show_bug.cgi?id=703791 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:N/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.