{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-7838 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2026-7838 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-7838 is a high-severity vulnerability in uvnc UltraVNC, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link."},"fix_prompt":"Check this codebase for CVE-2026-7838 and fix it if it is affected.\n\nWhat it is: CVE-2026-7838 is a high-severity vulnerability in uvnc UltraVNC, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.\nExploitation: There is no known exploitation of CVE-2026-7838 in the wild and no public exploit code.\n\nAffected product: uvnc UltraVNC. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-7838/ (Markdown: https://insights.sbomify.com/CVE-2026-7838/index.md)","id":"CVE-2026-7838","markdown":"https://insights.sbomify.com/CVE-2026-7838/index.md","name":"CVE-2026-7838","record":{"aliases":["GHSA-wxqv-4fpj-f62j"],"analysis":{"component_type":"desktop_application","fix_type":"upgrade","impacts":["code_execution"],"network_reachable":"yes","non_default_config":false,"product_category":"VNC client viewer","requires_auth":"none","summary":"A malicious VNC server can trigger a heap buffer overflow in UltraVNC viewer via integer overflow, potentially allowing remote code execution.","user_interaction":"required","vuln_class":"integer_overflow"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"securin","cpe":[{"product":"ultravnc","vendor":"uvnc"}],"cvss":{"score":8.7,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-787","name":"Out-of-bounds Write"},{"id":"CWE-190","name":"Integer Overflow or Wraparound"}],"description":"UltraVNC viewer through 1.8.2.2 contains an integer overflow leading to a heap buffer overflow in the RFB protocol failure-response parsing path. In vncviewer/ClientConnection.cpp, the 4-byte network-supplied reasonLen field (type CARD32) is passed as reasonLen+1 to CheckBufferSize(). Because both operands are unsigned 32-bit, a reasonLen of 0xFFFFFFFF overflows to 0, causing CheckBufferSize to allocate only 256 bytes. The subsequent ReadString(m_netbuf, reasonLen) call then performs ReadExact for the original 4 GiB length into that 256-byte heap buffer. This overflow is reachable via rfbConnFailed (auth-scheme negotiation) and rfbVncAuthFailed (post-handshake) message types without successful authentication. A malicious VNC server, or any man-in-the-middle on the RFB stream, can trigger this condition when the victim viewer connects, potentially resulting in remote code execution as the user running the viewer. The crash was confirmed with AddressSanitizer on a portable reproduction harness (heap-buffer-overflow WRITE at offset 256).","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":null,"headline":"UltraVNC viewer heap buffer overflow via integer overflow in RFB connection-failure reason length","id":"CVE-2026-7838","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"integer_overflow","year":"2026"},"n_packages":0,"n_references":3,"next":{"headline":"UltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin access","id":"CVE-2026-7839"},"packages":[],"prev":{"headline":"TOCTOU with root privilege in ad_flush","id":"CVE-2026-7837"},"products":["UltraVNC"],"published":"2026-07-01","related":[{"cvss_score":9.8,"headline":"Memory corruption in UltraVNC","id":"CVE-2019-8264","kev_date_added":null,"published":"2019-03-09"},{"cvss_score":9.8,"headline":"Memory corruption in UltraVNC","id":"CVE-2019-8265","kev_date_added":null,"published":"2019-03-09"},{"cvss_score":9.8,"headline":"Memory corruption in UltraVNC","id":"CVE-2019-8266","kev_date_added":null,"published":"2019-03-09"},{"cvss_score":9.8,"headline":"Memory corruption in UltraVNC","id":"CVE-2019-8280","kev_date_added":null,"published":"2019-03-09"},{"cvss_score":9.8,"headline":"Memory corruption in UltraVNC","id":"CVE-2018-15361","kev_date_added":null,"published":"2019-03-05"},{"cvss_score":9.8,"headline":"Integer overflow in UltraVNC","id":"CVE-2019-8260","kev_date_added":null,"published":"2019-03-05"},{"cvss_score":9.8,"headline":"Integer overflow in UltraVNC","id":"CVE-2019-8261","kev_date_added":null,"published":"2019-03-05"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-07-09","vendors":["uvnc"]},"summary":"A malicious VNC server can trigger a heap buffer overflow in UltraVNC viewer via integer overflow, potentially allowing remote code execution.","url":"https://insights.sbomify.com/CVE-2026-7838/"}