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:
- 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.
- 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[].
- 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.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- No SSVC decision: EchelonGraph has not assessed this CVECISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the BOD 26-04 block below.
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it