In the Linux kernel, the following vulnerability has been resolved:
pppoatm: ensure a writable skb header and linear data
In pppoatm_send(), LLC encapsulation checks whether there is sufficient
headroom for the 4-byte LLC header, but does not ensure that the skb header
is writable.
Normal transmit packets passing through ppp_start_xmit() have their header
unshared via skb_cow_head(). However, packets can also reach pppoatm_send()
via PPP channel bridging (PPPIOCBRIDGECHAN) without going through
ppp_start_xmit().
Use skb_cow_head() to ensure both sufficient headroom and a writable
header before pushing the LLC header.
While at it:
- Call pskb_may_pull(skb, 1) before inspecting skb->data[0] to prevent
out-of-bounds reads on zero-length or non-linear frames (e.g. from
bridging).
- Defer SC_COMP_PROT protocol compression until after pppoatm_may_send()
succeeds. This eliminates the temporary skb allocation on admission failure
and completely removes the fragile "undo" heuristic at the nospace label,
avoiding any risk of reading uninitialized headroom or performing an
unbalanced skb_push().
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.
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