CVE-2025-39833: Linux kernel · mISDN: hfcpci: Fix warning when deleting uninitialized timer
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux@6.8.0-136.136?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws@6.8.0-1060.63?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14@6.14.0-1018.18~24.04.1?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure@6.8.0-1062.69?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11@6.11.0-1018.18~24.04.1?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available that initializes the timer correctly and updates timeout handling. Users should apply the official kernel updates that include this fix. No additional mitigation is required beyond applying the patch.
Description
A vulnerability in the Linux kernel's mISDN hfcpci module caused a warning and potential system instability when unloading the module with CONFIG_DEBUG_OBJECTS_TIMERS enabled. The issue arises from deleting an uninitialized timer, leading to kernel warnings and splats. The fix involves properly initializing the timer with the DEFINE_TIMER macro and using mod_timer for timeout updates.
References
- ubuntu.com/security/CVE-2025-39833 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-39833 (opens in a new tab)
- git.kernel.org/linus/97766512a9951b9fd6fc97f1b93211642bb0b220 (opens in a new tab)
- git.kernel.org/stable/c/43fc5da8133badf17f5df250ba03b9d882254845 (opens in a new tab)
- git.kernel.org/stable/c/97766512a9951b9fd6fc97f1b93211642bb0b220 (opens in a new tab)