Bug 2541113 (CVE-2026-97964)

Summary: CVE-2026-97964 kernel: ppp_synctty: ensure a writeable skb header
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel's Point-to-Point Protocol (PPP) synchronous tty driver. When network packets are forwarded through PPP channel bridging, the driver prepends protocol header bytes to shared packet buffers without ensuring they are exclusively writable. This issue allows network traffic or a local user to overwrite data in shared network buffers, leading to data corruption or a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-09-25 10:49:31 UTC 
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.
Comment 1 gkamathe 2026-09-30 04:09:13 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97964.mbox