VYPR
← All advisories
Unrated severityOSV Advisory· Published Jan 30, 2019· Updated Aug 5, 2024

CVE-2018-20749

CVE-2018-20749

Description

LibVNC before 0.9.12 contains a heap out-of-bounds write vulnerability in libvncserver/rfbserver.c. The fix for CVE-2018-15127 was incomplete.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Heap out-of-bounds write in LibVNC's rfbserver.c due to incomplete fix for CVE-2018-15127, potentially leading to code execution.

Vulnerability

The vulnerability resides in libvncserver/rfbserver.c within the file transfer functionality. An incomplete fix for CVE-2018-15127 left a heap out-of-bounds write condition when processing specially crafted file transfer requests. All versions prior to 0.9.12 are affected [3][4].

Exploitation

An attacker with network access to a VNC server using LibVNC can send a malicious file transfer request with a crafted length value that bypasses the incomplete check. No authentication is required if the server allows unauthenticated connections. The attacker triggers the out-of-bounds write by causing a heap allocation and subsequent write that overflows the allocated buffer [3].

Impact

Successful exploitation could lead to remote code execution with the privileges of the VNC server process, or cause a denial of service. The vulnerability allows overwriting adjacent heap memory, potentially giving the attacker control over execution flow [3][4].

Mitigation

Fixed in LibVNC version 0.9.12 (released 2018-12-10) [4]. Users should upgrade to 0.9.12 or later. For systems that cannot upgrade, disabling file transfer or restricting network access to trusted clients may reduce risk.

References
  1. security - Re: libvnc and tightvnc vulnerabilities
  2. Error out in rfbProcessFileTransferReadBuffer if length can not be al… · LibVNC/libvncserver@15bb719

AI Insight generated on May 26, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

23

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

10

News mentions

0

No linked articles in our index yet.