CVE-2026-33023

HIGHNVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.8 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 79% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, when built with the --with-gdk-pixbuf2 option, a use-after-free vulnerability exists in load_with_gdkpixbuf() in loader.c. The cleanup path manually frees the sixel_frame_t object and its internal buffers without consulting the reference count, even though the object was created via the refcounted constructor sixel_frame_new() and exposed to the public callback. A callback that calls sixel_frame_ref(frame) to retain a logically valid reference will hold a dangling pointer after sixel_helper_load_image_file() returns, and any subsequent access to the frame or its fields triggers a use-after-free confirmed by AddressSanitizer. The root cause is a consistency failure between two cleanup strategies in the same codebase: sixel_frame_unref() is used in load_with_builtin() but raw free() is used in load_with_gdkpixbuf(). An attacker supplying a crafted image to any application built against libsixel with gdk-pixbuf2 support can trigger this reliably, potentially leading to information disclosure, memory corruption, or code execution. This issue has been fixed in version 1.8.7-r1.

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
51(Track*)
EG Risk 51/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity78% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
21%
KEV
Not listed

Published

April 14, 2026

Last Modified

July 25, 2026

Advisory Details (2)

Auto-updated Jun 10, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github.
github Patch Available🟡 PoC Available

Use-After-Free in load_with_gdkpixbuf() · Advisory · saitoha/libsixel · GitHub

https://github.com/saitoha/libsixel/security/advisories/GHSA-hr25-g2j6-qjw6
github_release Patch Available

v1.8.7-r1 security update

Patch available: saitoha/libsixel v1.8.7-r1

https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
libsixel1.10.3-1 ... 1:1.8.7-r2-1 (12 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
libsixel1.10.3-3 ... 1:1.8.7-r2-1 (9 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libsixel1.10.5-1 ... 1:1.8.7-r2-1 (8 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libsixel1.10.5-1 ... 1:1.8.7-6 (7 versions)1:1.8.7-r2-1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 5× in last 7d / 28× 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.

Showing the most recent 100 of 156 total refreshes for this CVE.

  1. 2026-09-13 16:47 UTCEPSS rescore
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  1. 2026-08-18 13:48 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2026-33023?
CVE-2026-33023 is a high vulnerability published on April 14, 2026. libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, when built with the --with-gdk-pixbuf2 option, a use-after-free vulnerability exists in loadwithgdkpixbuf() in loader.c. The cleanup path manually frees the sixelframet object and its…
When was CVE-2026-33023 disclosed?
CVE-2026-33023 was first published in the National Vulnerability Database on April 14, 2026, with the most recent update on July 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33023 actively exploited?
CVE-2026-33023 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 78.6% of all scored CVEs.
What is the CVSS score of CVE-2026-33023?
CVE-2026-33023 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2026-33023?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33023, 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.

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