# CVE-2026-68277: drm/dp/mst: fix OOB reads on 2-byte fields in sideband reply parsers

> Out-of-bounds reads in Linux kernel DisplayPort MST sideband parsers allow attackers to read adjacent memory or cause crashes.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Aug 2026
- **Updated:** 23 Aug 2026
- **Also known as:** BELL-CVE-2026-68277, DEBIAN-CVE-2026-68277, GHSA-5g47-cvq4-4x2c, UBUNTU-CVE-2026-68277

## What is CVE-2026-68277?

CVE-2026-68277 is a memory corruption vulnerability in Linux, published on 10 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:

drm/dp/mst: fix OOB reads on 2-byte fields in sideband reply parsers

Three sideband reply parsers read 16-bit fields as:

  val = (raw->msg[idx] << 8) | (raw->msg[idx+1]);

and check bounds only after the fact. When idx == raw->curlen,
raw->msg[idx+1] reads one byte past the received message data into
the following struct fields (curchunk_len, curchunk_idx, curlen).

Affected functions:
 - drm_dp_sideband_parse_enum_path_resources_ack()
   full_payload_bw_number and avail_payload_bw_number fields
 - drm_dp_sideband_parse_allocate_payload_ack()
   allocated_pbn field
 - drm_dp_sideband_parse_query_payload_ack()
   allocated_pbn field

Fix by using a single combined check (idx + 2 > curlen) before each
2-byte read. Since the check is strictly tighter than idx > curlen,
no separate step is needed.

[added fixes tag]

## Which versions are affected by CVE-2026-68277?


## How do I fix CVE-2026-68277?

Apply the vendor's patch.

## Is CVE-2026-68277 being exploited?

There is no known exploitation of CVE-2026-68277 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68277 and fix it if it is affected.

What it is: CVE-2026-68277 is a memory corruption vulnerability in Linux, published on 10 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-2026-68277 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-2026-68277/ (Markdown: https://insights.sbomify.com/CVE-2026-68277/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68277
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68277
- OSV: https://osv.dev/vulnerability/CVE-2026-68277

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68277/
Summaries are generated and may contain mistakes; the official description above is the record.