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CVE-2026-43981— Algernon: Race Condition in handle() shared LState

Quick assessment

Affected
xyproto algernon
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

algernon是Alexander F. Rødseth个人开发者的一个 Web 服务器。 Algernon 1.17.6之前版本存在竞争条件问题漏洞，该漏洞源于engine/luahandler.go中保护LoadCommonFunctions的sync.RWMutex在L.Push()和L.PCall()执行前释放，由于gopher-lua的LState明确不支持goroutine安全，并发请求竞争共享状态可能导致Lua虚拟机损坏。

AI Predicted 5.3 Difficulty: Easy EPSS 0.18% · P8

Affected Version Matrix 1

VendorProduct Version RangeStatus
xyproto algernon < 1.17.6 affected
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I. Basic Information for CVE-2026-43981

Vulnerability Information
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Vulnerability Title
Algernon: Race Condition in handle() shared LState
Source: CVE Program / CVE List V5
Vulnerability Description
Algernon is a small self-contained pure-Go web server. Prior to 1.17.6, in engine/luahandler.go, the sync.RWMutex protecting LoadCommonFunctions is released before L.Push() and L.PCall() execute. Since gopher-lua's LState is explicitly not goroutine-safe, concurrent requests race on the shared state causing Lua VM corruption. The Go race detector confirms this immediately under modest concurrency (ab -n 1000 -c 100). This vulnerability is fixed in 1.17.6.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
使用共享资源的并发执行不恰当同步问题(竞争条件)
Source: CVE Program / CVE List V5
Vulnerability Title
algernon 竞争条件问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
algernon是Alexander F. Rødseth个人开发者的一个 Web 服务器。 Algernon 1.17.6之前版本存在竞争条件问题漏洞，该漏洞源于engine/luahandler.go中保护LoadCommonFunctions的sync.RWMutex在L.Push()和L.PCall()执行前释放，由于gopher-lua的LState明确不支持goroutine安全，并发请求竞争共享状态可能导致Lua虚拟机损坏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
xyproto algernon < 1.17.6 -

II. Public POCs for CVE-2026-43981

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III. Intelligence Information for CVE-2026-43981

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Vendor Advisories for CVE-2026-43981 (1)

Other References for CVE-2026-43981 (1)

Same Patch Batch · xyproto · 2026-05-26 · 7 CVEs total

CVE-2026-45721 9.0 CRITICAL Algernon: handler.lua discovery walks parent directories above the server root
CVE-2026-48126 8.2 HIGH Algernon: Host header path traversal in --domain mode reads files and runs Lua from parent
CVE-2026-45728 7.5 HIGH Algernon: Single-file mode unconditionally enables debug mode
CVE-2026-46430 4.3 MEDIUM Algernon: Auto-refresh SSE event server binds to all interfaces by default on Linux/macOS
CVE-2026-46431 4.3 MEDIUM Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: *
CVE-2026-43982 Algernon: Path traversal file write via savein()

IV. Related Vulnerabilities

Same product: algernon
Same vendor: xyproto
Same weakness: CWE-362

V. Comments for CVE-2026-43981

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