Security readout for executives and security teams
Plain-English summary
Qt 6.9.0 contains a low-severity memory-safety flaw in HTTP/2 POST processing. A timing race between uploading a request body and receiving an HTTP error can access freed memory. Ordinary HTTP is unaffected. Qt reports the issue fixed in 6.9.1.
Executive priority
Treat this as a routine, targeted update rather than an emergency. Confirm whether Qt 6.9.0 is deployed, then upgrade exposed applications through normal patch management. Escalate priority if the affected HTTP/2 POST path is business-critical or processes untrusted interactions.
Technical view
CVE-2025-5991 is a CWE-416 use-after-free in QtNetwork's QHttp2ProtocolHandler. It arises from a race involving QHttp2Stream body uploads for HTTP/2 POST requests and simultaneous HTTP error-response handling. The supplied CVSS 4.0 score is 2.1, with local attack vector and high attack complexity.
Likely exposure
Exposure is limited to applications using Qt 6.9.0 and QtNetwork HTTP/2 POST handling. Applications using other Qt versions, or only ordinary HTTP handling, are described as unaffected. The bundle does not identify specific downstream applications or deployment patterns.
Exploitation context
The source bundle provides no evidence of active exploitation, and the CVE is not listed as KEV. The race condition and high-complexity CVSS assessment suggest exploitation depends on specific timing and request-processing conditions. No public exploit capability is established by the supplied evidence.
Researcher notes
The core issue is object-lifetime handling during concurrent stream upload and error processing. The supplied material does not establish reliable triggering, concrete crash behavior, exploitability beyond the CVSS assessment, or affected downstream products. Analysis should therefore remain scoped to Qt 6.9.0 and the documented HTTP/2 path.
Mitigation direction
- Upgrade affected Qt 6.9.0 deployments to Qt 6.9.1 or a later vendor-supported release.
- Prioritize applications that send HTTP/2 POST requests with uploaded request bodies.
- If immediate upgrading is impossible, consult Qt guidance before considering temporary HTTP/2 restrictions.
Validation and detection
- Inventory applications and dependencies for Qt 6.9.0, including bundled or statically linked copies.
- Confirm whether each affected application uses QtNetwork for HTTP/2 POST body uploads.
- Verify rebuilt or updated applications resolve Qt to version 6.9.1 or later.
- Run regression tests covering HTTP/2 POST uploads and concurrent HTTP error responses.
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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CWE-416: Exact CWE lookup
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Open ATT&CK lookupCVE-2025-5991 mapping review
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Open ATT&CK lookup- Severity
- Low
- CVSS
- 2.1 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L
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.
SSVC decision data
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:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L——TQtCVulnerability scoring details
Base CVSS 4.0 score
2.1LowVector: CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L
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.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://codereview.qt-project.org/c/qt/qtbase/+/643777CVE reference, TQtC
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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.