Unauthenticated code execution via UDP message overflow
Published Jul 16, 2025 · Updated Apr 7, 2026
Stack-based buffer overflow in Achat Software AChat Chat Server 0.150 allows remote attackers to execute code via UDP port 9256. The UDP message parser accepts an oversized A0000000002#Main payload without sufficient bounds checking, overwriting the SEH handler. The default configuration exposes the unauthenticated service on the local network, and successful exploitation depends on racing two stack-overflowing threads.
Summary
What happened
Stack-based buffer overflow in Achat Software AChat Chat Server 0.150 allows remote attackers to execute code via UDP port 9256. The UDP message parser accepts an oversized A0000000002#Main payload without sufficient bounds checking, overwriting the SEH handler. The default configuration exposes the unauthenticated service on the local network, and successful exploitation depends on racing two stack-overflowing threads.
The record
- CVE
- CVE-2025-34127
- Published
- Jul 16, 2025
- Updated
- Apr 7, 2026
- Vendor
- Achat Software
- Product
- AChat Chat Server
- Classifications
- CWE-121, CWE-94, CAPEC-137, CAPEC-100, T1210
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 16, 2025CVE publishedPublication date reported by the CVE source.
- Apr 7, 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.
- Affected versionversion=0.150
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- AChat 0.150 beta7 Remote Buffer Overflowfunctional · unverified
- AChat Unicode SEH Buffer Overflow Metasploit modulefunctional · demonstrated
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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