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Fencer Vulns
high 8.8

CVE-2021-33477 json

rxvt-unicode 9.22, rxvt 2.7.10, mrxvt 0.5.4, and Eterm 0.9.7 allow (potentially remote) code execution because of improper handling of cert…

published 2021-05-20 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-20180

cvss
8.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.1%
EPSS 4.1% chance of exploitation in 30 days, percentile 90%
public exploits
0
none known

Summary

rxvt-unicode 9.22, rxvt 2.7.10, mrxvt 0.5.4, and Eterm 0.9.7 allow (potentially remote) code execution because of improper handling of certain escape sequences (ESC G Q). A response is terminated by a newline.

Patch / fix

  • eterm Debian 14, Debian 12 0.9.6-6.1
  • rxvt-unicode Debian 14, Debian 13, Debian 12 9.22-11

debian advisories DEBIAN-CVE-2021-33477

  • rxvt-unicode Ubuntu Pro 16.04 LTS 9.21-1ubuntu0.1~esm1
  • rxvt-unicode Ubuntu Pro 18.04 LTS 9.22-3ubuntu0.1~esm1
  • rxvt-unicode Ubuntu Pro 20.04 LTS 9.22-6ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2021-33477

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

  • rxvt-unicode openSUSE Tumbleweed 9.30-2.1
  • rxvt-unicode Package Hub 15 SP4, Package Hub 15 SP3, openSUSE Leap 15.4 +1 more 9.26-bp154.2.3.1

opensuse advisories openSUSE-SU-2024:12386-1openSUSE-SU-2022:10222-1

  • mrxvt Alpine 3.11, Alpine 3.10 0.5.4-r8
  • mrxvt Alpine 3.24, Alpine 3.23, Alpine 3.22 +9 more 0.5.4-r9
  • rxvt-unicode Alpine 3.10 9.22-r7
  • rxvt-unicode Alpine 3.11 9.22-r8
  • rxvt-unicode Alpine 3.13 9.22-r10
  • rxvt-unicode Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 9.26-r0

alpine advisories ALPINE-CVE-2021-33477

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

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-2021-33477 updated cvss 7.0

rxvt-unicode: possible remote code execution

  • 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

4.09% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • openwall.com https://www.openwall.com/lists/oss-security/2021/05/17/1 referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com https://packetstormsecurity.com/files/162621/rxvt-2.7.0-rxvt-unicode-9.22-Code-Execution.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.5 AV:N/AC:L/Au:S/C:P/I:P/A:P

Classification

Weakness
  • CWE-755 Improper Handling of Exceptional Conditions

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.