Security readout for executives and security teams
Plain-English summary
A malformed zero-length authentication checksum can make the Linux kernel dereference a null pointer while processing SUNRPC Kerberos authentication. A successful attack can crash or disrupt an affected system, causing service downtime. The supplied CVSS score is 7.5 because the issue is network-reachable, requires no privileges or user interaction, and affects availability rather than data confidentiality or integrity.
Executive priority
Prioritize remediation for exposed SUNRPC infrastructure because the documented outcome is remotely triggered system disruption. Accelerate patching where outages would affect critical operations. Maintain normal risk-based scheduling for systems without reachable SUNRPC services, while confirming vendor-specific exposure because the supplied affected-version data is incomplete.
Technical view
In xdr_stream_decode_opaque_auth(), a zero-length checksum sets checksum.data to NULL. gss_krb5_verify_mic_v2() subsequently accesses that pointer, causing a kernel null-pointer dereference. The kernel fix rejects checksums shorter than XDR_UNIT. The supplied vector is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Likely exposure
Exposure is most relevant to affected Linux systems running network-accessible SUNRPC services that process Kerberos-backed GSS authentication. The bundle lists affected Linux versions but does not clearly define complete version ranges or distribution package status. Confirm exposure using each distribution’s kernel advisory and whether the cited stable fix is included.
Exploitation context
The supplied record describes network-based, low-complexity, unauthenticated availability impact. It does not establish code execution, data theft, or privilege escalation. The CVE is not identified as CISA KEV in the bundle, and no cited source reports active exploitation or a public exploit. Treat exploitation status as unconfirmed.
Researcher notes
The failure chain is specifically zero-length opaque-auth checksum handling followed by MIC verification. The fix enforces checksum.len >= XDR_UNIT before the pointer is consumed. Four Linux stable commits are cited, likely covering separate maintained branches. The bundle does not provide reliable branch-to-version mapping, exploit evidence, crash reproducibility details, or distribution backport status.
Mitigation direction
- Install a vendor-supported kernel update containing the cited zero-length checksum validation fix.
- Prioritize internet-facing or untrusted-network SUNRPC systems using Kerberos authentication.
- Restrict unnecessary network access to SUNRPC services until affected systems are updated.
- Check Linux distribution advisories for exact package versions and reboot requirements.
Validation and detection
- Inventory kernel versions on systems providing SUNRPC services.
- Determine whether RPCSEC_GSS or Kerberos authentication is enabled and network-reachable.
- Confirm the installed kernel contains the applicable cited stable fix.
- Verify patched systems booted into the updated kernel after maintenance.
- Monitor kernel logs for null-pointer faults involving the named SUNRPC and GSS functions.
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
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ATT&CK lookup starting points
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CVE-2025-40129 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/81cec07d303186d0d8c623ef8b5ecd3b81e94cf6CVE reference, Linux
- https://git.kernel.org/stable/c/affc03d44921f493deaae1d33151e3067a6f9f8fCVE reference, Linux
- https://git.kernel.org/stable/c/ab9a70cd2386a0d70c164b0905dd66bc9af52e77CVE reference, Linux
- https://git.kernel.org/stable/c/6df164e29bd4e6505c5a2e0e5f1e1f6957a16a42CVE 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.