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NVD / CVE Program· CNA Linux

CVE-2025-37953: sch_htb: make htb_deactivate() idempotent

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 31ff70ad39485698cf779f2078132d80b57f6c07, 3769478610135e82b262640252d90f6efb05be71, 6.1.139.

Low priority for now. Upgrade to Linux Linux 31ff70ad39485698cf779f2078132d80b57f6c07, 3769478610135e82b262640252d90f6efb05be71, 6.1.139 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: sch_htb: make htb_deactivate() idempotent Alan reported a NULL pointer dereference in htb_next_rb_node() after we made htb_qlen_notify() idempotent. It turns out in the following case it introduced some regression: htb_dequeue_tree(): |-> fq_codel_dequeue() |-> qdisc_tree_reduce_backlog() |-> htb_qlen_notify() |-> htb_deactivate() |-> htb_next_rb_node() |-> htb_deactivate() For htb_next_rb_node(), after calling the 1st htb_deactivate(), the clprio[prio]->ptr could be already set to NULL, which means htb_next_rb_node() is vulnerable here. For htb_deactivate(), although we checked qlen before calling it, in case of qlen==0 after qdisc_tree_reduce_backlog(), we may call it again which triggers the warning inside. To fix the issues here, we need to: 1) Make htb_deactivate() idempotent, that is, simply return if we already call it before. 2) Make htb_next_rb_node() safe against ptr==NULL. Many thanks to Alan for testing and for the reproducer.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
May 20, 2025
Updated
Jun 17, 2026
EPSS
0.1% · 9th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux11.0
  • linux linux kernel6.1.138
  • linux linux kernel6.12.28
  • linux linux kernel6.14.6
  • linux linux kernel6.15
  • linux linux kernel6.6.90

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • e6b45f4de763b00dc1c55e685e2dd1aaf525d3c1 and later · before 99ff8a20fd61315bf9ae627440a5ff07d22ee153affected · git
    • 32ae12ce6a9f6bace186ca7335220ff59b6cc3cd and later · before a9945f7cf1709adc5d2d31cb6cfc85627ce299a8affected · git
    • 967955c9e57f8eebfccc298037d4aaf3d42bc1c9 and later · before c2d25fddd867ce20a266806634eeeb5c30cb520caffected · git
    • 73cf6af13153d62f9b76eff422eea79dbc70f15e and later · before c928dd4f6bf0c25c72b11824a1e9ac9bd37296a0affected · git
    • bbbf5e0f87078b715e7a665d662a2c0e77f044ae and later · before 31ff70ad39485698cf779f2078132d80b57f6c07affected · git
    • 0a188c0e197383683fd093ab1ea6ce9a5869a6ea and later · before 98cd7ed92753090a714f0802d4434314526fe61daffected · git
    • a61f1b5921761fbaf166231418bc1db301e5bf59 and later · before c4792b9e38d2f61b07eac72f10909fa76130314baffected · git
    • 5ba8b837b522d7051ef81bacf3d95383ff8edce5 and later · before 3769478610135e82b262640252d90f6efb05be71affected · git
    • 6.1.138 and later · before 6.1.139affected · semver
    • 6.6.90 and later · before 6.6.91affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.140-16.1.140-1
Debian:13linuxbefore 6.12.29-16.12.29-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-37950May 20, 2025 · ocfs2: fix panic in failed foilio allocation
    22Monitor
  • ← EarlierCVE-2025-37951May 20, 2025 · drm/v3d: Add job to pending list if the reset was skipped
    22Monitor
  • Later →CVE-2025-37955May 20, 2025 · virtio-net: free xsk_buffs on error in virtnet_xsk_pool_enable()
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux31ff70ad39485698cf779f2078132d80b57f6c07Vendor (CNA)
Linux Linux3769478610135e82b262640252d90f6efb05be71Vendor (CNA)
Linux Linux6.1.139Vendor (CNA)
Linux Linux6.12.29Vendor (CNA)
Linux Linux6.14.7Vendor (CNA)
Linux Linux6.6.91Vendor (CNA)
Linux Linux98cd7ed92753090a714f0802d4434314526fe61dVendor (CNA)
Linux Linux99ff8a20fd61315bf9ae627440a5ff07d22ee153Vendor (CNA)
Linux Linuxa9945f7cf1709adc5d2d31cb6cfc85627ce299a8Vendor (CNA)
Linux Linuxc2d25fddd867ce20a266806634eeeb5c30cb520cVendor (CNA)
Linux Linuxc4792b9e38d2f61b07eac72f10909fa76130314bVendor (CNA)
Linux Linuxc928dd4f6bf0c25c72b11824a1e9ac9bd37296a0Vendor (CNA)
debian:linux6.1.140-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (8 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records