{"id":"CVE-2026-44988","state":"PUBLISHED","title":"LibVNCClient Tight Gradient decoding allows malicious server-triggered heap/stack OOB writes","description":"LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter. When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit 5b270544b85233668b98161323297d418a8f5fd1.","publishedAt":"2026-05-27T14:26:50.063Z","updatedAt":"2026-05-29T15:16:13.607Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["LibVNC libvncserver"],"affected":[{"vendor":"LibVNC","product":"libvncserver","versions":[{"version":"<= 0.9.15","status":"affected"}]}],"references":["https://github.com/LibVNC/libvncserver/security/advisories/GHSA-jcc5-8wj4-7c58","https://github.com/LibVNC/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1"],"weaknesses":["CWE-787"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/44xxx/CVE-2026-44988.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-44988","state":"PUBLISHED","datePublished":"2026-05-27T14:26:50.063Z","dateUpdated":"2026-05-29T15:16:13.607Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-08T16:23:33.265Z"},"containers":{"cna":{"title":"LibVNCClient Tight Gradient decoding allows malicious server-triggered heap/stack OOB writes","descriptions":[{"lang":"en","value":"LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter. When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit 5b270544b85233668b98161323297d418a8f5fd1."}],"affected":[{"vendor":"LibVNC","product":"libvncserver","versions":[{"version":"<= 0.9.15","status":"affected"}]}],"references":[{"url":"https://github.com/LibVNC/libvncserver/security/advisories/GHSA-jcc5-8wj4-7c58","name":"https://github.com/LibVNC/libvncserver/security/advisories/GHSA-jcc5-8wj4-7c58","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/LibVNC/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1","name":"https://github.com/LibVNC/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-787","lang":"en","description":"CWE-787: Out-of-bounds Write","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-05-27T14:26:50.063Z"},"source":{"advisory":"GHSA-jcc5-8wj4-7c58","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-29T03:55:55.774539Z","id":"CVE-2026-44988","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-29T15:16:13.607Z"}}]}}}