CVE-2025-21844 — smb: client: Add check for next_buffer in receive_encrypted_standard()
In the Linux kernel, the following vulnerability has been resolved: smb: client: Add check for next_buffer in receive_encrypted_standard() Add check for the return value of cifs_buf_get() and cifs_small_buf_get() in receive_encrypted_standard() to prevent null pointer dereference.
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 0.6% (30-day exploitation probability)+7
- Technical severity (medium)+3
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)
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).
- Apply the fixed version or the patch documented under Remediation.
- 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 |
≥ 858e73ff25639a0cc1f6f8d2587b62c045867e41 and < f618aeb6cad2307e48a641379db610abcf593edfversion 6.7≥ 6.6.8 and < 6.6.80≥ 6.1.69 and < 6.1.130≥ 5.15.150 and < 5.15.179≥ 5.10.211 and < 5.10.235≥ eec04ea119691e65227a97ce53c0da6b9b74b0b7 and < 860ca5e50f73c2a1cef7eefc9d39d04e275417f7≥ eec04ea119691e65227a97ce53c0da6b9b74b0b7 and < 554736b583f529ee159aa95af9a0cbc12b5ffc96 and 4 more≥ eec04ea119691e65227a97ce53c0da6b9b74b0b7 and < a9b0b4b29877cb4dc5d0842b59b5ccbacddb85bd≥ 534733397da26de0303057ce0b93a22bda150365 and < 9e5d99a4cf2e23c716b44862975548415fae5391≥ 9f528a8e68327117837b5e28b096f52af4c26a05 and < 24e8e4523d3071bc5143b0db9127d511489f7b3b≥ b03c8099a738a04d2343547ae6a04e5f0f63d3fa and < f277e479eea3d1aa18bc712abe1d2bf3dece2e30 |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
≥ 6.1.69 and < 6.1.130version 6.14-rc3version 6.14-rc2version 6.14-rc1version 5.15.150version 5.10.211≥ 6.13 and < 6.13.5≥ 6.7 and < 6.12.17 and 1 more≥ 6.6.8 and < 6.6.80 |
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 |
|---|---|---|---|---|---|
| 7.5 | CVSS 3.1 | High | 3.9 | 3.6 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database |
| 7.5 | CVSS 3.1 | High | — | — | Linux via CVE Program (cve.org) e CISA ADP |
| 5.5 | CVSS 3.1 | Medium | 1.8 | 3.6 | nvd@nist.gov via NIST National Vulnerability Database |
| 5.5 | CVSS 3.1 | Medium | 1.8 | 3.6 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database |
| 5.5 | CVSS 3.1 | Medium | — | — | CISA-ADP via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov) 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.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
- 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
- CVSS changed · 5.5
- Source status changed · → Modified
- Record created in this database
- 2025
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
11 on the record
- git.kernel.org/stable/c/f618aeb6cad2307e48a641379db610abcf593edf
- git.kernel.org/stable/c/554736b583f529ee159aa95af9a0cbc12b5ffc96
- git.kernel.org/stable/c/860ca5e50f73c2a1cef7eefc9d39d04e275417f7
- git.kernel.org/stable/c/a9b0b4b29877cb4dc5d0842b59b5ccbacddb85bd
- git.kernel.org/stable/c/f277e479eea3d1aa18bc712abe1d2bf3dece2e30
- git.kernel.org/stable/c/24e8e4523d3071bc5143b0db9127d511489f7b3b
- git.kernel.org/stable/c/9e5d99a4cf2e23c716b44862975548415fae5391
- lists.debian.org/debian-lts-announce/2025/05/msg00045.html
- lists.debian.org/debian-lts-announce/2025/05/msg00030.html
- cert-portal.siemens.com/productcert/html/ssa-784472.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 11h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 11h
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 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-2025-21844 is "smb: client: Add check for next_buffer in receive_encrypted_standard()", rated Medium. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.62% 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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