CVE-2025-39877: Linux kernel · mm/damon/sysfs: fix use-after-free in state_show()
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in 3858c44341ad49dc7544b19cc9f9ecffaa7cc50e : update Linux kernel when convenient.
Data as of 5 Nov 2026, 21:49 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-05.
- Patch
- Available – fixed in 3858c44341ad49dc7544b19cc9f9ecffaa7cc50e, 3260a3f0828e06f5f13fac69fb1999a6d60d9cff, 60d7a3d2b985a395318faa1d88da6915fad11c19 +2
Exploitation evidence
Disclosed: evidence found.
CVE published 23 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 5 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in– |
Description
In the Linux kernel, the following vulnerability has been resolved: mm/damon/sysfs: fix use-after-free in state_show() state_show() reads kdamond->damon_ctx without holding damon_sysfs_lock. This allows a use-after-free race: CPU 0 CPU 1 ----- ----- state_show() damon_sysfs_turn_damon_on() ctx = kdamond->damon_ctx; mutex_lock(&damon_sysfs_lock); damon_destroy_ctx(kdamond->damon_ctx); kdamond->damon_ctx = NULL; mutex_unlock(&damon_sysfs_lock); damon_is_running(ctx); /* ctx is freed */ mutex_lock(&ctx->kdamond_lock); /* UAF */ (The race can also occur with damon_sysfs_kdamonds_rm_dirs() and damon_sysfs_kdamond_release(), which free or replace the context under damon_sysfs_lock.) Fix by taking damon_sysfs_lock before dereferencing the context, mirroring the locking used in pid_show(). The bug has existed since state_show() first accessed kdamond->damon_ctx.
References
- git.kernel.org/stable/c/3858c44341ad49dc7544b19cc9f9ecffaa7cc50e (opens in a new tab)
- git.kernel.org/stable/c/60d7a3d2b985a395318faa1d88da6915fad11c19 (opens in a new tab)
- git.kernel.org/stable/c/26d29b2ac87a2989071755f9828ebf839b560d4c (opens in a new tab)
- git.kernel.org/stable/c/4e87f461d61959647464a94d11ae15c011be58ce (opens in a new tab)
- git.kernel.org/stable/c/3260a3f0828e06f5f13fac69fb1999a6d60d9cff (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00008.html (opens in a new tab)