Square Wire up to 6.4.4/7.0.0-alpha03 Protobuf Reader denial of service

Summaryinfo

A vulnerability was found in Square Wire up to 6.4.4/7.0.0-alpha03. It has been classified as problematic. The impacted element is the function ByteArrayProtoReader32.internalNextLengthDelimited of the component Protobuf Reader. The manipulation leads to denial of service. This vulnerability is documented as CVE-2026-63126. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Square Wire up to 6.4.4/7.0.0-alpha03. It has been rated as problematic. This issue affects the function ByteArrayProtoReader32.internalNextLengthDelimited of the component Protobuf Reader. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-63126 since 07/15/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 6.4.5 or 7.0.0-alpha04 eliminates this vulnerability.

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Productinfo

Vendor

• Square

Name

• Wire

Version

• 6.4.0
• 6.4.1
• 6.4.2
• 6.4.3
• 6.4.4
• 7.0.0-alpha03

Website

• Product: https://github.com/square/wire/

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