Security readout for executives and security teams
Plain-English summary
A Linux kernel RxRPC parsing flaw can mishandle an untrusted, undersized ticket or response length. The resulting unsigned arithmetic error may disrupt affected systems. Available evidence supports an availability risk, not data theft or modification.
Executive priority
Treat as a high-priority availability issue for network-exposed systems using the affected kernel functionality. Accelerate vendor patch review and exposure validation, but do not characterize it as actively exploited based on current evidence.
Technical view
The rxgk YFS decoder subtracts fixed field sizes from attacker-influenced unsigned lengths without first confirming sufficient data. This can underflow during ticket and response decoding. The kernel fix adds two length prechecks and replaces a numeric structure length with sizeof().
Likely exposure
The supplied record marks Linux kernel versions beginning with 6.16 and extending toward 6.17 as affected. Practical exposure depends on whether a distribution kernel includes the vulnerable RxRPC code and whether relevant RxRPC/rxgk functionality processes untrusted network input.
Exploitation context
The CVSS vector describes network reachability, low complexity, no privileges, and no user interaction, with availability as the identified impact. The CVE is not in KEV, and the supplied sources provide no evidence of active exploitation or a public exploit.
Researcher notes
The central defect is insufficient bounds validation before unsigned subtraction in rxgk_yfs_decode_ticket(). The stated remediation covers two extraction points during token and response decoding. The supplied version data is not detailed enough to map every distribution kernel reliably; use vendor backport information or commit presence.
Mitigation direction
- Apply a vendor-supported kernel update containing the referenced stable fixes.
- Prioritize systems using RxRPC or rxgk with untrusted network exposure.
- If updating is delayed, consult distribution guidance for supported temporary mitigations.
- Restrict unnecessary network access to relevant services where operationally feasible.
Validation and detection
- Inventory kernel versions and distribution package revisions across potentially exposed systems.
- Confirm whether vendor kernels contain either referenced stable fix.
- Verify updated systems boot and run the intended kernel package.
- Test relevant RxRPC workloads for normal operation after updating.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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Credential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2025-39962 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6LinuxVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/71571e187106631a8127f2dde780f35caa358d33CVE reference, Linux
- https://git.kernel.org/stable/c/2429a197648178cd4dc930a9d87c13c547460564CVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.