CVE-2026-63803

Local privilege escalation via unsynchronized PPP timers

Published Jul 19, 2026 · Updated Jul 19, 2026

Use-after-free in Linux Kernel hdlc_ppp allows local users to escalate privileges by racing synchronous PPP protocol teardown. detach_hdlc_protocol() frees hdlc->state without synchronizing embedded LCP, IPCP, and IPV6CP timers, allowing a running ppp_timer callback to dereference freed state and its lock. The path requires CAP_NET_ADMIN and an HDLC WAN device configured for synchronous PPP; the freed-memory access also causes a kernel oops or panic.

CVSS severity7.8
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux Kernel hdlc_ppp allows local users to escalate privileges by racing synchronous PPP protocol teardown. detach_hdlc_protocol() frees hdlc->state without synchronizing embedded LCP, IPCP, and IPV6CP timers, allowing a running ppp_timer callback to dereference freed state and its lock. The path requires CAP_NET_ADMIN and an HDLC WAN device configured for synchronous PPP; the freed-memory access also causes a kernel oops or panic.

The record

CVE
CVE-2026-63803
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <508a0139d3bf60f6a03d2fbfb63a89a9463d983a
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5a84398101bf9f11e84b176343e4e3ba83e668c0
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8308122bc9c065b1f376e081ed300129a2ac9545
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a594debfd4e7ec39413647458907f689ef57fd2f
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c64dbef1c0fbd36f9530aa75112acdf6a6d3cfd8
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c78a4e41ab5ead6193ad8a2dd92e8906bae659fa
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ce8f9ddca0c9f217342a8b49efd309aa35b81a36
  8. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <508a0139d3bf60f6a03d2fbfb63a89a9463d983a; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5a84398101bf9f11e84b176343e4e3ba83e668c0; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8308122bc9c065b1f376e081ed300129a2ac9545; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <a594debfd4e7ec39413647458907f689ef57fd2f; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c64dbef1c0fbd36f9530aa75112acdf6a6d3cfd8; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c78a4e41ab5ead6193ad8a2dd92e8906bae659fa; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ce8f9ddca0c9f217342a8b49efd309aa35b81a36; version=2.6.12

Published CVSS scores

7.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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