ppp_synctty: ensure a writeable skb header

Answer in brief

CVE-2026-97964 records a Unknown severity vulnerability in ppp_synctty: ensure a writeable skb header. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 25, 2026Updated Sep 25, 2026Source checked Sep 25, 2026First seen by HOL Sep 25, 2026Material review Sep 25, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=4cf476ced45d7f12df30a68e833b263e7a2202d1 <3af7797fbabc84992e0ca5ad2bc0ca8537d053ef \|\| >=4cf476ced45d7f12df30a68e833b263e7a2202d1 <0996c3e6bcc6ae08cb371ed43648c9f7f748ae6e \|\| >=4cf476ced45d7f12df30a68e833b263e7a2202d1 <15d0a6c9a42df2d745c37510dba828f6dbe60d9f \|\| >=4cf476ced45d7f12df30a68e833b263e7a2202d1 <8aaeb56aff2a557a88f83ae866da2c91ad247e59	3af7797fbabc84992e0ca5ad2bc0ca8537d053ef, 0996c3e6bcc6ae08cb371ed43648c9f7f748ae6e, 15d0a6c9a42df2d745c37510dba828f6dbe60d9f, 8aaeb56aff2a557a88f83ae866da2c91ad247e59
Linux/Linuxgeneric	5.11	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 3af7797fbabc84992e0ca5ad2bc0ca8537d053ef if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 25, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: ppp_synctty: ensure a writeable skb header ppp_sync_txmunge() checks headroom before prepending the address and control bytes, but does not ensure that the skb header is writable. A received skb can reach this function through PPP channel bridging without passing through ppp_start_xmit(), which calls skb_cow_head(). For example, a PPPoE frame may share its buffer with a clone queued to an AF_PACKET socket. If it is bridged to a synchronous tty channel, the address/control bytes can overwrite data still visible to that socket. Use skb_cow_head() to ensure both sufficient headroom and a writable header.

Quoted source text, attributed separately from HOL analysis.