CVE-2026-61695 Wire Swift runtime: negative LENGTH_DELIMITED length in skipGroup() crashes any protobuf-decoding service
Attackers can crash Swift services decoding untrusted protobuf data by exploiting a negative length check in the Wire library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-61695?
CVE-2026-61695 is a high-severity vulnerability in square wire, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Wire provides gRPC and protocol buffers for Android, Kotlin, Swift, and Java. Prior to 6.4.1 and 7.0.0-alpha04, Wire's Swift runtime ProtoReader.skipGroup(expectedEndTag:unknownFieldsWriter:) accepts a negative length for a LENGTH_DELIMITED field inside an unknown START_GROUP field. ProtoReader.readData() forwards the negative count to ReadBuffer.readData(count:), whose upper-bound-only check permits the value to reach Foundation Data(bytes:count:) and trigger an unrecoverable process trap instead of a catchable ProtoDecoder.Error. Any Swift process decoding untrusted protobuf bytes can be crashed without authentication, user interaction, or knowledge of the target schema. This issue is fixed in versions 6.4.1 and 7.0.0-alpha04.
Weakness: CWE-129
Which versions are affected by CVE-2026-61695?
2 open source packages ship an affected version, including github.com/square/wire.
| Package | Affected | Fixed in |
|---|---|---|
github.com/square/wire SwiftURL | All versions | 6.4.1 |
github.com/square/wire SwiftURL | All versions | 6.4.1 |
How do I fix CVE-2026-61695?
Upgrade github.com/square/wire to 6.4.1 or later.
Is CVE-2026-61695 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-61695 exists.
Sources
Also known as GHSA-86wm-r4c5-2rc9.