CVE-2026-68278 drm/dp/mst: fix buffer overflows in sideband chunk accumulation
A malicious DP MST device can trigger buffer overflows in the Linux kernel sideband handler, potentially leading to code execution or system crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68278?
CVE-2026-68278 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 buffer overflows in sideband chunk accumulation
drm_dp_sideband_append_payload() has three related bugs when processing device-provided sideband reply data:
1. Zero-length curchunk_len underflow: msg_len is a 6-bit field taken directly from the DP sideband header. If a device sends msg_len=0, curchunk_len is set to zero. The condition (curchunk_idx >= curchunk_len) is immediately true, and curchunk_len-1 wraps to 255 (u8 underflow). drm_dp_msg_data_crc4() reads 255 bytes from chunk[48], then memcpy() writes 255 bytes into msg[], both far out of bounds.
2. chunk[48] overflow: curchunk_len can reach 63 (6-bit field). chunk[] is only 48 bytes. Multi-iteration payload assembly appends 16-byte blocks until curchunk_idx reaches curchunk_len, writing up to 15 bytes past the end of chunk[] into msg[].
3. msg[256] overflow: each chunk contributes (curchunk_len-1) bytes to msg[]. No check ensures curlen + (curchunk_len-1) stays within msg[256], so the memcpy can spill into adjacent struct fields.
All three are reachable from any DP MST device that can forge sideband reply messages on a physical connection.
Which versions are affected by CVE-2026-68278?
How do I fix CVE-2026-68278?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-68278 being exploited?
There is no known exploitation of CVE-2026-68278 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68278, DEBIAN-CVE-2026-68278, GHSA-4w62-3fjj-vmpc, UBUNTU-CVE-2026-68278.