Out-of-Bounds Read Vulnerability in NetSurf's libnsbmp Library
CVE-2026-111139

6.8MEDIUM

Key Information:

Vendor

Netsurf

Status
Libnsbmp
Vendor
CVE Published:
15 October 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-111139?

The libnsbmp library, used by the NetSurf browser, contains an out-of-bounds read vulnerability in the bmp_decode_mask() function. By supplying a specially crafted ICO file with a bitmap width that is not a multiple of 8, attackers can exploit this flaw to read one byte past the image buffer. This heap over-read can lead to application crashes and potential information disclosure for any software reliant on the libnsbmp library for image decoding.

Affected Version(s)

libnsbmp 0 <= 0.1.7

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-111139 - Proof of Concept

References

https://hackmd.io/@haind-pwn/libnsbmp-rle-absolute-pad-an...
technical-descriptionexploit
https://github.com/netsurf-browser/libnsbmp/blob/ea063c9f...
technical-description
https://download.netsurf-browser.org/libs/releases/libnsb...
product

CVSS V4

Score:
6.8
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

HaiND from the Post and Telecommunication Institute of Technology
.