CVE-2025-37953sch_htb: make htb_deactivate() idempotent
- 5.5MediumCVSS base score
- 0.19%Exploitation in 30 daysEPSS · top 91% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
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.
Timeline
ID reserved
By Linux
- 34 days later
· 34 days later
Published
- 12 months later
· 12 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Analyzed | 3.1 | Medium5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.19% · top 91% of all CVEs (13 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.
Affected products
- affected e6b45f4de763b00dc1c55e685e2dd1aaf525d3c1 – < 99ff8a20fd61315bf9ae627440a5ff07d22ee153
- affected 32ae12ce6a9f6bace186ca7335220ff59b6cc3cd – < a9945f7cf1709adc5d2d31cb6cfc85627ce299a8
- affected 967955c9e57f8eebfccc298037d4aaf3d42bc1c9 – < c2d25fddd867ce20a266806634eeeb5c30cb520c
- affected 73cf6af13153d62f9b76eff422eea79dbc70f15e – < c928dd4f6bf0c25c72b11824a1e9ac9bd37296a0
- affected bbbf5e0f87078b715e7a665d662a2c0e77f044ae – < 31ff70ad39485698cf779f2078132d80b57f6c07
- affected 0a188c0e197383683fd093ab1ea6ce9a5869a6ea – < 98cd7ed92753090a714f0802d4434314526fe61d
- affected a61f1b5921761fbaf166231418bc1db301e5bf59 – < c4792b9e38d2f61b07eac72f10909fa76130314b
- affected 5ba8b837b522d7051ef81bacf3d95383ff8edce5 – < 3769478610135e82b262640252d90f6efb05be71
- affected 6.1.138 – < 6.1.139
- affected 6.6.90 – < 6.6.91
- affected 6.12.28 – < 6.12.29
- affected 6.14.6 – < 6.14.7
References
References9
- https://git.kernel.org/stable/c/99ff8a20fd61315bf9ae627440a5ff07d22ee153 (opens in a new tab)
- https://git.kernel.org/stable/c/a9945f7cf1709adc5d2d31cb6cfc85627ce299a8 (opens in a new tab)
- https://git.kernel.org/stable/c/c2d25fddd867ce20a266806634eeeb5c30cb520c (opens in a new tab)
- https://git.kernel.org/stable/c/c928dd4f6bf0c25c72b11824a1e9ac9bd37296a0 (opens in a new tab)
- https://git.kernel.org/stable/c/31ff70ad39485698cf779f2078132d80b57f6c07 (opens in a new tab)
- https://git.kernel.org/stable/c/98cd7ed92753090a714f0802d4434314526fe61d (opens in a new tab)
- https://git.kernel.org/stable/c/c4792b9e38d2f61b07eac72f10909fa76130314b (opens in a new tab)
- https://git.kernel.org/stable/c/3769478610135e82b262640252d90f6efb05be71 (opens in a new tab)
- https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2025-15902 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2025-37953)Record last updated .