# CVE-2026-68458: binder: cache secctx size before release zeroes it

> A logic error in the Linux kernel binder driver allows out-of-bounds writes by using a zeroed security context size, potentially enabling privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-68458, DEBIAN-CVE-2026-68458, GHSA-h3w9-f79p-226g, UBUNTU-CVE-2026-68458

## What is CVE-2026-68458?

CVE-2026-68458 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

binder: cache secctx size before release zeroes it

binder_transaction() bounds the scatter-gather buffer area with
sg_buf_end_offset and subtracts the aligned LSM context size because
the secctx is written at the tail of that area.  The subtraction reads
lsmctx.len, but that field has already been cleared by the time the
line runs:

    security_secid_to_secctx(secid, &lsmctx)   /* lsmctx.len set */
    lsmctx_aligned_size = ALIGN(lsmctx.len, sizeof(u64))
    extra_buffers_size += lsmctx_aligned_size
    ...
    security_release_secctx(&lsmctx)            /* memset zeroes len */
    ...
    sg_buf_end_offset = sg_buf_offset + extra_buffers_size
                        - ALIGN(lsmctx.len, sizeof(u64)) /* ALIGN(0,8) */

security_release_secctx() does memset(cp, 0, sizeof(*cp)), so lsmctx.len
reads back as 0 and the subtraction contributes nothing, leaving
sg_buf_end_offset too large by the aligned secctx size on every
transaction to a txn_security_ctx node.

Each BINDER_TYPE_PTR object then derives buf_left = sg_buf_end_offset -
sg_buf_offset as the sole upper bound on its copy, so the inflated end
offset lets the copy run into the bytes that already hold the secctx.

The aligned size must therefore be cached before release rather than
re-read from the now-cleared field.  Fix by caching it in
lsmctx_aligned_size at function scope when it is first computed and
subtracting lsmctx_aligned_size instead of re-reading lsmctx.len after
release.  Reuse the same value for the earlier buf_offset computation.

## Which versions are affected by CVE-2026-68458?


## How do I fix CVE-2026-68458?

Apply the vendor's patch.

## Is CVE-2026-68458 being exploited?

There is no known exploitation of CVE-2026-68458 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68458 and fix it if it is affected.

What it is: CVE-2026-68458 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-68458 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-68458/ (Markdown: https://insights.sbomify.com/CVE-2026-68458/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68458
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68458
- OSV: https://osv.dev/vulnerability/CVE-2026-68458

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68458/
Summaries are generated and may contain mistakes; the official description above is the record.