CVE-2025-39847: Linux kernel · ppp: fix memory leak in pad_compress_skb
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in 4844123fe0b853a4982c02666cb3fd863d701d50 : update Linux kernel when convenient.
Data as of 5 Nov 2026, 21:35 UTC
Rated Medium by Threat Radar's AI analysis · 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 4844123fe0b853a4982c02666cb3fd863d701d50, 631fc8ab5beb9e0ec8651fb9875b9a968e7b4ae4, 87a35a36742df328d0badf4fbc2e56061c15846c +5
Exploitation evidence
Disclosed: evidence found.
CVE published 19 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
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AI-suggested
A fix is available and has been applied in the Linux kernel. Users should update to a kernel version that includes the patch identified by the fixed commit hashes. No additional mitigation is required once the patch is applied.
Description
A memory leak vulnerability in the Linux kernel's ppp module was fixed by correcting the pad_compress_skb() function. The issue occurred when alloc_skb() failed inside pad_compress_skb(), causing the function to return NULL without freeing the original skb buffer. This led to a lost reference and a memory leak. The fix aligns pad_compress_skb() semantics with realloc(), ensuring the old skb is only freed if allocation and compression succeed, preventing memory leaks.
References
- git.kernel.org/stable/c/9ca6a040f76c0b149293e430dabab446f3fc8ab7 (opens in a new tab)
- git.kernel.org/stable/c/87a35a36742df328d0badf4fbc2e56061c15846c (opens in a new tab)
- git.kernel.org/stable/c/0b21e9cd4559102da798bdcba453b64ecd7be7ee (opens in a new tab)
- git.kernel.org/stable/c/1d8b354eafb8876d8bdb1bef69c7d2438aacfbe8 (opens in a new tab)
- git.kernel.org/stable/c/85c1c86a67e09143aa464e9bf09c397816772348 (opens in a new tab)
- git.kernel.org/stable/c/631fc8ab5beb9e0ec8651fb9875b9a968e7b4ae4 (opens in a new tab)
- git.kernel.org/stable/c/33a5bac5f14772730d2caf632ae97b6c2ee95044 (opens in a new tab)
- git.kernel.org/stable/c/4844123fe0b853a4982c02666cb3fd863d701d50 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00008.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00007.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-032379.html (opens in a new tab)