Wire: Unauthenticated decoder crash via 32-bit length integer overflow in ByteArrayProtoReader32 (incomplete fix of CVE-2026-45799)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-63126: 0.82% estimated exploitation activity in the next 30 days; percentile 57.39 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Wire's protobuf decoders did not consistently validate attacker-controlled length-delimited sizes against the current reader bounds before computing cursor, limit, or pointer positions. In the Kotlin runtime, ProtoAdapter.decode(ByteArray) and ProtoAdapter.decode(ByteString) use the ProtoReader32 fast path implemented by ByteArrayProtoReader32. In ByteArrayProtoReader32.internalNextLengthDelimited(), Wire read an untrusted varint length into an Int and rejected only negative values. A length such as 2147483647 is non-negative, so it passed that check, but pos + length overflowed the signed 32-bit cursor and produced a negative limit. The following if (limit pushedLimit) guard did not catch this because the overflowed value was negative. That invalid limit then reached string, bytes, skip, and scalar-reading paths as an invalid byte count or invalid range. Instead of failing as a checked decode error such as IOException, malformed input could throw unchecked runtime exceptions…

Published by the source

17 Sep 2026, 14:52 UTC

Last modified by the source

17 Sep 2026, 15:00 UTC

Source last checked

26 Oct 2026, 16:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9rm7-3qhh-h2mc

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9rm7-3qhh-h2mc

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# Patch Next advisory brief: CVE-2026-63126

Advisory: Wire: Unauthenticated decoder crash via 32-bit length integer overflow in ByteArrayProtoReader32 (incomplete fix of CVE-2026-45799)
IDs: CVE-2026-63126, GHSA-9rm7-3qhh-h2mc
Record: https://patchnext.com/advisories/cve-2026-63126 (revision 2, source checked 26 Oct 2026, 16:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: com.squareup.wire:wire-runtime 7.0.0-alpha04, 6.4.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven com.squareup.wire:wire-runtime: affected <= 6.4.4; >= 7.0.0-alpha01, < 7.0.0-alpha04; fixed in 7.0.0-alpha04, 6.4.5

## Suggested inspection (read-only)
- Maven com.squareup.wire:wire-runtime: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on com.squareup.wire:wire-runtime.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9rm7-3qhh-h2mc (OSV record GHSA-9rm7-3qhh-h2mc lists affected ranges: Maven com.squareup.wire:wire-runtime >=0 =7.0.0-alpha01 <7.0.0-alpha04 (fixed))
- Verified: https://github.com/advisories/GHSA-9rm7-3qhh-h2mc (GitHub-reviewed advisory GHSA-9rm7-3qhh-h2mc lists affected ranges: Maven com.squareup.wire:wire-runtime >=0 =7.0.0-alpha01 <7.0.0-alpha04)

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