In libsixel 1.8.6, sixel_encoder_output_without_macro (called from sixel_encoder_encode_frame in encoder.c) has a double free.

published 2022-02-19 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-33360

cvss: 6.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.0%; EPSS 1.0% chance of exploitation in 30 days, percentile 61%
public exploits: 0; none known

Exploit prediction

0.95% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/saitoha/libsixel/issues/158 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	6.5	CVSS:3.1/AV:N/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

CWE-415 Double Free

References

github.com /saitoha/libsixel/issues/158
exploit, issue-tracking, third-party-advisory

Sources

CVE List CVE-2021-46700
NVD CVE-2021-46700

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.

Summary