High severity · published Sep 16, 2026
CVE-2026-63126
Wire: Unauthenticated decoder crash via 32-bit length integer overflow in ByteArrayProtoReader32 (incomplete fix of CVE-2026-45799)
7.5
CVSS
0.8%
EPSS
No
On KEV
Description
Wire provides gRPC and protocol buffers for Android, Kotlin, Swift, and Java. Prior to 6.4.5 and 7.0.0-alpha04, Wire protobuf readers do not consistently validate attacker-controlled lengths against the current logical message boundary before advancing cursors, pointers, limits, slices, or allocations. In Kotlin, ProtoAdapter.decode(ByteArray) and ProtoAdapter.decode(ByteString) use ByteArrayProtoReader32.internalNextLengthDelimited(), where a positive oversized length can wrap pos + length to a negative limit and escape the existing negative-length check. Related ProtoReader, ReadBuffer.readVarint(), ReadBuffer.verifyAdditional(count:), packed-repeated, nested-message, and ProtoDecoder.decodeSizeDelimited(_:from:) paths can cross logical boundaries, perform pointer arithmetic, reserve capacity, or convert an unrepresentable size before proving the requested bytes exist. An attacker who supplies malformed protobuf bytes can cause unchecked exceptions, traps, out-of-bounds behavior, or excessive allocation, resulting in denial of service without known confidentiality, integrity, or code-execution impact. This issue is fixed in versions 6.4.5 and 7.0.0-alpha04.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 57% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WI
wire · square
< 6.4.5; >= 7.0.0-alpha01, < 7.0.0-alpha04 · source: vendor
Affected product
WI
wire
square
More from wire
7.5
CVE-2026-61695
Wire Swift runtime: negative LENGTH_DELIMITED length in skipGroup() crashes any protobuf-decoding service
7.5
CVE-2026-45799
Wire: skipGroup() missing negative-length check allows 10-byte payload to crash any Wire-decoding service
5.8
CVE-2024-58103
Square Wire before 5.2.0 does not enforce a recursion limit on nested groups in ByteArrayProtoReader32.kt and ProtoReader.kt