CVE-2026-63803: hdlc_ppp: sync per-proto timers before freeing hdlc state

highCVSS 8.4CVE-2026-63803

CSIRTS triage

vendor: Linux product: hdlc_pppOther

What: This vulnerability syncs per-proto timers before freeing hdlc state.
Who is affected: Deployments using the hdlc_ppp protocol.
Urgency: Remediation is necessary to prevent potential issues, although exploitation is not currently reported.
Action: Sync per-proto timers before freeing hdlc state.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 8.4
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63803

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-638030.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-63803	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for hdlc_ppp

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-63803: In the Linux kernel, the following vulnerability has been resolved: hdlc_ppp: sync per-proto t…nvd · 2026-07-19