{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-33020", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-03-17T17:22:14.667Z", "datePublished": "2026-04-14T21:53:00.388Z", "dateUpdated": "2026-04-15T13:30:47.463Z"}, "containers": {"cna": {"title": "libsixel: Integer Overflow in write_png_to_file() leads to Heap-based Buffer Overflow", "problemTypes": [{"descriptions": [{"cweId": "CWE-122", "lang": "en", "description": "CWE-122: Heap-based Buffer Overflow", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-190", "lang": "en", "description": "CWE-190: Integer Overflow or Wraparound", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.1, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H", "version": "3.1"}}], "references": [{"name": "https://github.com/saitoha/libsixel/security/advisories/GHSA-2xgm-4x47-2x2p", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-2xgm-4x47-2x2p"}, {"name": "https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1", "tags": ["x_refsource_MISC"], "url": "https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1"}], "affected": [{"vendor": "saitoha", "product": "libsixel", "versions": [{"version": "< 1.8.7-r1", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-04-14T21:53:00.388Z"}, "descriptions": [{"lang": "en", "value": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow which leads to a heap buffer overflow via sixel_frame_convert_to_rgb888() in frame.c, where allocation size and pointer offset computations for palettised images (PAL1, PAL2, PAL4) are performed using int arithmetic before casting to size_t. For images whose pixel count exceeds INT_MAX / 4, the overflow produces an undersized heap allocation for the conversion buffer and a negative pointer offset for the normalization sub-buffer, after which sixel_helper_normalize_pixelformat() writes the full image data starting from the invalid pointer, causing massive heap corruption confirmed by ASAN. An attacker providing a specially crafted large palettised PNG can corrupt the heap of the victim process, resulting in a reliable crash and potential arbitrary code execution.\nThis issue has been fixed in version 1.8.7-r1."}], "source": {"advisory": "GHSA-2xgm-4x47-2x2p", "discovery": "UNKNOWN"}}, "adp": [{"references": [{"url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-2xgm-4x47-2x2p", "tags": ["exploit"]}], "metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-04-15T13:30:43.489988Z", "id": "CVE-2026-33020", "options": [{"Exploitation": "poc"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-15T13:30:47.463Z"}}]}}

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{"cveTags": [], "descriptions": [{"lang": "en", "value": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow which leads to a heap buffer overflow via sixel_frame_convert_to_rgb888() in frame.c, where allocation size and pointer offset computations for palettised images (PAL1, PAL2, PAL4) are performed using int arithmetic before casting to size_t. For images whose pixel count exceeds INT_MAX / 4, the overflow produces an undersized heap allocation for the conversion buffer and a negative pointer offset for the normalization sub-buffer, after which sixel_helper_normalize_pixelformat() writes the full image data starting from the invalid pointer, causing massive heap corruption confirmed by ASAN. An attacker providing a specially crafted large palettised PNG can corrupt the heap of the victim process, resulting in a reliable crash and potential arbitrary code execution.\nThis issue has been fixed in version 1.8.7-r1."}], "id": "CVE-2026-33020", "lastModified": "2026-04-15T14:16:15.307", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.1, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.2, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-04-14T22:16:30.543", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1"}, {"source": "security-advisories@github.com", "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-2xgm-4x47-2x2p"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-2xgm-4x47-2x2p"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-122"}, {"lang": "en", "value": "CWE-190"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "libsixel: libsixel: Arbitrary code execution via crafted palettised PNG image processing", "id": "2458500", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2458500"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.1", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H", "status": "draft"}, "cwe": "CWE-190", "details": ["A flaw was found in libsixel. An integer overflow vulnerability in the `sixel_frame_convert_to_rgb888()` function can lead to a heap buffer overflow when processing specially crafted large palettised PNG images. An attacker can exploit this by providing a malicious image, which causes heap corruption in the victim's process. This can result in a denial of service due to a reliable crash and potentially allow for arbitrary code execution."], "mitigation": {"lang": "en:us", "value": "Avoid processing untrusted or suspicious image files with applications that use libsixel. If possible, restrict the sources of images processed by affected applications to trusted origins."}, "name": "CVE-2026-33020", "public_date": "2026-04-14T21:53:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-33020\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-33020\nhttps://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1\nhttps://github.com/saitoha/libsixel/security/advisories/GHSA-2xgm-4x47-2x2p"], "statement": "Important: A heap buffer overflow flaw in libsixel, triggered by processing specially crafted palettised PNG images, can lead to denial of service and potentially arbitrary code execution. This vulnerability requires user interaction, as an attacker must provide a malicious image to the victim's process. Red Hat products utilizing libsixel for image processing may be affected if they handle untrusted image input.", "threat_severity": "Moderate"}