CVE-2025-21760 — ndisc: extend RCU protection in ndisc_send_skb()
In the Linux kernel, the following vulnerability has been resolved: ndisc: extend RCU protection in ndisc_send_skb() ndisc_send_skb() can be called without RTNL or RCU held. Acquire rcu_read_lock() earlier, so that we can use dev_net_rcu() and avoid a potential UAF.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 36.8% (30-day exploitation probability)+15
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- EPSS ahead of 98% of scored CVEs: prioritize it in the patch queue.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < 10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1version 2.6.26≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < ed6ae1f325d3c43966ec1b62ac1459e2b8e45640≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < 04e05112f10354ffc3bb6cc796d553bab161594c≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < 789230e5a8c1097301afc802e242c79bc8835c67≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < ae38982f521621c216fc2f5182cd091f4734641d≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < a9319d800b5701e7f5e3fa71a5b7c4831fc20d6d≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < e24d225e4cb8cf108bde00b76594499b98f0a74d and 1 more≥ 1762f7e88eb34f653b4a915be99a102e347dd45e and < 4d576202b90b1b95a7c428a80b536f91b8201bcc |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
≥ 2.6.26 and < 5.4.291version 6.14-rc2version 6.14-rc1≥ 6.13 and < 6.13.4≥ 6.7 and < 6.12.16≥ 6.2 and < 6.6.79≥ 5.16 and < 6.1.129≥ 5.11 and < 5.15.179 and 1 more≥ 5.5 and < 5.10.235 |
Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.1 | CVSS 3.1 | High | 2.2 | 5.9 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database |
| 8.1 | CVSS 3.1 | High | — | — | Linux via CVE Program (cve.org) e CISA ADP |
| 7.8 | CVSS 3.1 | High | 1.8 | 5.9 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database |
| 7.8 | CVSS 3.1 | High | — | — | GitHub, Inc. via GitHub Security Advisories |
| 7.8 | CVSS 3.1 | High | — | — | CISA-ADP via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- SSVC assessment updated
- Record published
- Fix documented
- Affected products added · linux/linux kernel
- CVSS changed · 8.1
- Source status changed · → Modified
- Record created in this database
- 2025
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 14, 2026 – Oct 14, 2026
References
16 on the record
- git.kernel.org/stable/c/789230e5a8c1097301afc802e242c79bc8835c67
- git.kernel.org/stable/c/ed6ae1f325d3c43966ec1b62ac1459e2b8e45640
- git.kernel.org/stable/c/e24d225e4cb8cf108bde00b76594499b98f0a74d
- git.kernel.org/stable/c/a9319d800b5701e7f5e3fa71a5b7c4831fc20d6d
- git.kernel.org/stable/c/04e05112f10354ffc3bb6cc796d553bab161594c
- git.kernel.org/stable/c/4d576202b90b1b95a7c428a80b536f91b8201bcc
- git.kernel.org/stable/c/10a1f3fece2f0d23a3a618b72b2b4e6f408ef7d1
- git.kernel.org/stable/c/ae38982f521621c216fc2f5182cd091f4734641d
- lists.debian.org/debian-lts-announce/2025/05/msg00030.html
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- cert-portal.siemens.com/productcert/html/ssa-784472.html
- github.com/advisories/GHSA-wm97-xp23-f4x4
- nvd.nist.gov/vuln/detail/CVE-2025-21760
- lists.debian.org/debian-lts-announce/2025/03/msg00028.html
- cert-portal.siemens.com/productcert/html/ssa-265688.html
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 8h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 8h
- Unknown CVE-2026-98428 ALSA: usb: 6fire: Avoid embedded URBs 1d
- Unknown CVE-2026-98431 RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency 1d
- Unknown CVE-2026-98430 RDMA/efa: Keep admin queues alive while IRQ is registered 1d
- Unknown CVE-2026-98429 RDMA/efa: Keep EQ resources alive while IRQ is registered 1d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2025-21760 is "ndisc: extend RCU protection in ndisc_send_skb()", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.1 describes technical severity. EPSS 36.85% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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