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CVE Record

CVE-2025-21832: block: don't revert iter for -EIOCBQUEUED

In the Linux kernel, the following vulnerability has been resolved: block: don't revert iter for -EIOCBQUEUED blkdev_read_iter() has a few odd checks, like gating the position and count adjustment on whether or not the result is bigger-than-or-equal to zero (where bigger than makes more sense), and not checking the return value of blkdev_direct_IO() before doing an iov_iter_revert(). The latter can lead to attempting to revert with a negative value, which when passed to iov_iter_revert() as an unsigned value will lead to throwing a WARN_ON() because unroll is bigger than MAX_RW_COUNT. Be sane and don't revert for -EIOCBQUEUED, like what is done in other spots.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel block-device read handling flaw. Under a specific asynchronous direct I/O error path, the kernel can try to undo more iterator state than is valid, triggering a kernel warning. The sources do not state data theft, privilege escalation, remote attack, or active exploitation.

Executive priority

Treat this as a patch-management item, not an emergency, unless internal evidence shows crashes or instability on critical Linux hosts. There is no cited active exploitation, but kernel defects can affect availability and shared infrastructure.

Technical view

blkdev_read_iter() could call iov_iter_revert() after blkdev_direct_IO() returned -EIOCBQUEUED. That negative value can be treated as a large unsigned revert length, causing WARN_ON because it exceeds MAX_RW_COUNT. Stable kernel commits change the block layer to avoid reverting for -EIOCBQUEUED.

Likely exposure

Exposure is limited to systems running affected Linux kernel versions identified in the CVE record and using the relevant block-device direct I/O path. Downstream distributions may backport fixes, so package version alone may not prove vulnerability.

Exploitation context

The bundle provides no exploit, no CVSS score, no CWE, and KEV is false. Based on the cited description, the demonstrated impact is a kernel warning condition, not confirmed code execution, privilege escalation, or active exploitation.

Researcher notes

Evidence is narrow: the CVE text describes an iterator revert bug and stable commits, but omits CVSS, exploitability prerequisites, and concrete impact beyond WARN_ON. Avoid overstating risk without vendor-specific advisories or reproducer evidence.

Mitigation direction

  • Apply vendor or distribution kernel updates that include the referenced stable fixes.
  • For Debian LTS systems, review the cited Debian LTS advisory and update accordingly.
  • Prioritize internet-facing or multi-tenant Linux hosts after confirming affected kernels.
  • If no vendor package is available, monitor vendor guidance for backported fixes.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and container hosts.
  • Map running kernels to vendor advisories and the referenced stable commits.
  • Check whether distribution kernels have backported the fix despite older version labels.
  • Review kernel logs for related WARN_ON events during block-device direct I/O operations.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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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CVE-2025-21832 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

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.

0CVSS vectors
3Timeline events
1ADP providers
7Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux3e1f941dd9f33776b3df4e30f741fe445ff773f3, 3e1f941dd9f33776b3df4e30f741fe445ff773f3, 3e1f941dd9f33776b3df4e30f741fe445ff773f3, 3e1f941dd9f33776b3df4e30f741fe445ff773f3, 3e1f941dd9f33776b3df4e30f741fe445ff773f3unaffected
LinuxLinux5.17, 0, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.