# CVE-2021-46935: linux: In the Linux kernel, the following vulnerability has been resolved:  binder: fix async_free_space accounting for empt...

CVE-2021-46935 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-46935, released February 27, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-46935
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Feb 27, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  binder: fix async_free_space accounting for empty parcels  In 4.13, commit 74310e06be4d ("android: binder: Move buffer out of area shared with user space") fixed a kernel structure visibility issue. As part of that patch, sizeof(void *) was used as the buffer size for 0-length data payloads so the driver could detect abusive clients sending 0-length asynchronous transactions to a server by enforcing limits on async_free_size.  Unfortunately, on the "free" side, the accounting of async_free_space did not add the sizeof(void *) back. The result was that up to 8-bytes of async_free_space were leaked on every async transaction of 8-bytes or less.  These small transactions are uncommon, so this accounting issue has gone undetected for several years.  The fix is to use "buffer_size" (the allocated buffer size) instead of "size" (the logical buffer size) when updating the async_free_space during the free operation. These are the same except for this corner case of asynchronous transactions with payloads < 8 bytes.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.15.15-1 | [DEBIAN-CVE-2021-46935](https://patchblox.com/security/data/fix/linux/debian-cve-2021-46935.md) | Feb 27, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.15.15-1 | [DEBIAN-CVE-2021-46935](https://patchblox.com/security/data/fix/linux/debian-cve-2021-46935.md) | Feb 27, 2024 |
| Linux | linux Debian 14 | 5.15.15-1 | [DEBIAN-CVE-2021-46935](https://patchblox.com/security/data/fix/linux/debian-cve-2021-46935.md) | Feb 27, 2024 |

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