CVE-2026-40492Public exploitNetwork attack vector

Code execution via mismatched XWD pixel metadata

Published Apr 18, 2026 · Updated Apr 18, 2026

Heap buffer overflow in the XWD codec in HappySeaFox SAIL before commit 36aa5c7 allows remote attackers to execute arbitrary code. xwd_private_read_pixels resolves a one-byte indexed pixel buffer from pixmap_depth but casts it to uint32_t when attacker-controlled bits_per_pixel is 32, reading and writing four bytes per pixel. Processing a crafted XWD image is the required gate; the demonstrated overwrite corrupts adjacent heap memory, while arbitrary code execution is the advisory's bounded worst-case impact.

CVSS severity9.8
Critical
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in the XWD codec in HappySeaFox SAIL before commit 36aa5c7 allows remote attackers to execute arbitrary code. xwd_private_read_pixels resolves a one-byte indexed pixel buffer from pixmap_depth but casts it to uint32_t when attacker-controlled bits_per_pixel is 32, reading and writing four bytes per pixel. Processing a crafted XWD image is the required gate; the demonstrated overwrite corrupts adjacent heap memory, while arbitrary code execution is the advisory's bounded worst-case impact.

The record

CVE
CVE-2026-40492
Published
Apr 18, 2026
Updated
Apr 18, 2026
Vendor
HappySeaFox
Product
SAIL
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

HappySeaFox · SAILversion=< 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02

Published CVSS scores

9.8GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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