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CVE-2025-38001— net_sched: hfsc: Address reentrant enqueue adding class to eltree twice

Quick assessment

Affected
Linux Linux
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于hfsc中重复插入类到eltree，可能导致无限循环或UAF。

CVSS 7.8 · High EPSS 0.52% · P43

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 20

VendorProduct Version RangeStatus
Linux Linux 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< e5bee633cc276410337d54b99f77fbc1ad8801e5 affected
37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< 6672e6c00810056acaac019fe26cdc26fee8a66c affected
37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< 2c928b3a0b04a431ffcd6c8b7d88a267124a3a28 affected
37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< a0ec22fa20b252edbe070a9de8501eef63c17ef5 affected
37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< 295f7c579b07b5b7cf2dffe485f71cc2f27647cb affected
37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< 2f2190ce4ca972051cac6a8d7937448f8cb9673c affected
37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< 4e38eaaabfb7fffbb371a51150203e19eee5d70e affected
37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea< 39ed887b1dd2d6b720f87e86692ac3006cc111c8 affected
… +12 more rows
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I. Basic Information for CVE-2025-38001

Vulnerability Information
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Vulnerability Title
net_sched: hfsc: Address reentrant enqueue adding class to eltree twice
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Address reentrant enqueue adding class to eltree twice Savino says: "We are writing to report that this recent patch (141d34391abbb315d68556b7c67ad97885407547) [1] can be bypassed, and a UAF can still occur when HFSC is utilized with NETEM. The patch only checks the cl->cl_nactive field to determine whether it is the first insertion or not [2], but this field is only incremented by init_vf [3]. By using HFSC_RSC (which uses init_ed) [4], it is possible to bypass the check and insert the class twice in the eltree. Under normal conditions, this would lead to an infinite loop in hfsc_dequeue for the reasons we already explained in this report [5]. However, if TBF is added as root qdisc and it is configured with a very low rate, it can be utilized to prevent packets from being dequeued. This behavior can be exploited to perform subsequent insertions in the HFSC eltree and cause a UAF." To fix both the UAF and the infinite loop, with netem as an hfsc child, check explicitly in hfsc_enqueue whether the class is already in the eltree whenever the HFSC_RSC flag is set. [1] https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=141d34391abbb315d68556b7c67ad97885407547 [2] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L1572 [3] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L677 [4] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L1574 [5] https://lore.kernel.org/netdev/8DuRWwfqjoRDLDmBMlIfbrsZg9Gx50DHJc1ilxsEBNe2D6NMoigR_eIRIG0LOjMc3r10nUUZtArXx4oZBIdUfZQrwjcQhdinnMis_0G7VEk=@willsroot.io/T/#u
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于hfsc中重复插入类到eltree，可能导致无限循环或UAF。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea ~ e5bee633cc276410337d54b99f77fbc1ad8801e5 -
Linux Linux 5.0 -

II. Public POCs for CVE-2025-38001

# POC Description Source Link Shenlong Link
1 CVE-2025-38001: Linux HFSC Eltree Use-After-Free - Debian 12 PoC https://github.com/0xdevil/CVE-2025-38001 POC Details
2 None https://github.com/khoatran107/cve-2025-38001 POC Details
3 None https://github.com/ngobao2002/CVE-2025-38001-test POC Details
4 Public exploit for CVE-2025-38001 https://github.com/boeseejykbtanke348/CVE-2025-38001 POC Details
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III. Intelligence Information for CVE-2025-38001

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Patches & Fixes for CVE-2025-38001 (8)

Security Blog Posts for CVE-2025-38001 (1)

Other References for CVE-2025-38001 (1)

Same Patch Batch · Linux · 2025-06-06 · 3 CVEs total

CVE-2025-38002 7.8 HIGH io_uring/fdinfo: grab ctx->uring_lock around io_uring_show_fdinfo()
CVE-2025-38000 7.8 HIGH sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue()

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-38001

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