GHSA-wxqv-4fpj-f62j · 深刻度： high — UltraVNC viewer through 1.8.2.2 contains an integer overflow leading to a heap buffer overflow in...
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).
総合評価: CVE-2026-7838 は中リスク（59.3/100）。CVSS 深刻度は高。悪用される可能性が高い（EPSS 1.40%、69 パーセンタイル） 推奨対応: 影響資産を整理し、修補計画に組み込んでください。
リスクは変動します。再評価に基づき、本ページの表示内容を更新しています。
EPSS は日次で悪用されやすさの相対度合いを推定します。パーセンタイルは採点済み CVE の中での相対位置（高いほど相対的に深刻）を示します。
| # | 日付 | 旧 EPSS スコア | 新 EPSS スコア | Δ（新 − 旧） |
|---|---|---|---|---|
| 1 | 2026-07-09 | 1.15% | 1.40% | +0.25% |
| 2 | 2026-07-01 | — | 1.15% | — |
EPSS の全履歴 （全 2 件）
この CVE の CVSS 指標。
| ベーススコア | バージョン | 深刻度 | ベクトル | 悪用しやすさ | 影響 | スコアの出典 |
|---|---|---|---|---|---|---|
| 8.7 | 4.0 | HIGH |
|
— | — | 33c584b5-0579-4c06-b2a0-8d8329fcab9c |
| 8.8 | 3.1 | HIGH |
|
2.8 | 5.9 | 33c584b5-0579-4c06-b2a0-8d8329fcab9c |
GHSA-wxqv-4fpj-f62j · 深刻度： high — UltraVNC viewer through 1.8.2.2 contains an integer overflow leading to a heap buffer overflow in...
| URL | タグ |
|---|---|
| https://github.com/ultravnc/UltraVNC | Product |
| https://uvnc.com/ | Product Release Notes |
| https://www.securin.io/zero-days/cve-2026-7838-heap-overflow-viewer-reasonlen-integer-overflow-ultravnc |