CVE-2026-43981Network attack vector

Unauthenticated service interruption via shared Lua state race

Published May 26, 2026 · Updated May 26, 2026

Race condition in Algernon before 1.17.6 allows remote attackers to interrupt service through concurrent requests to Lua handlers. The handle path in engine/luahandler.go releases the sync.RWMutex before L.Push() and L.PCall(), allowing requests to race on a shared, non-goroutine-safe LState. The server must be using Lua, and modest unauthenticated request concurrency is sufficient to corrupt the Lua VM and cause denial of service.

CVSS severity8.2
High
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Algernon before 1.17.6 allows remote attackers to interrupt service through concurrent requests to Lua handlers. The handle path in engine/luahandler.go releases the sync.RWMutex before L.Push() and L.PCall(), allowing requests to race on a shared, non-goroutine-safe LState. The server must be using Lua, and modest unauthenticated request concurrency is sufficient to corrupt the Lua VM and cause denial of service.

The record

CVE
CVE-2026-43981
Published
May 26, 2026
Updated
May 26, 2026
Vendor
xyproto
Product
Algernon
Classifications
CWE-362, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 26, 2026CVE publishedPublication date reported by the CVE source.
  2. May 26, 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=< 1.17.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

xyproto · Algernonversion=< 1.17.6

Published CVSS scores

8.2GitHub, Inc.CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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