HighVulnerabilityLLM-specific

CVE-2026-21521: Copilot information disclosure via improper neutralization of escape sequences

Source: NVD(opens in a new tab)
Identifier: CVE-2026-21521
Published: January 22, 2026
Record updated: October 9, 2026

Known exploitation: Not listed in the CISA Known Exploited Vulnerabilities catalog at the last check.
EPSS: 0.6%

Summary

CVE-2026-21521 is classified as CWE-150, Improper Neutralization of Escape, Meta, or Control Sequences, in Copilot. The source states that an unauthorized attacker can disclose information over a network. NVD has not yet provided an assessment, and the affected software configurations list is not populated in the source.

Mitigation

The source does not state a fix yet. Check the original advisory for updates.

Details

Scores and exploitation

CVSS score: 7.4(high)
EPSS: 0.6%Estimated probability that this CVE is exploited in the next 30 days, from the FIRST Exploit Prediction Scoring System. Read on November 4, 2026.

Weaknesses and techniques

Weakness (CWE): CWE-150

Affected

Vendors: Microsoft

Classification

Attack type: Other
Attack sophistication: Moderate
AI component targeted: Inference
Impact: Confidentiality
Labels: security

How this record was produced

Summaries, mitigations and labels on this page are generated automatically from the source. The linked source is authoritative. The source gives this advisory a description and no title, so the title above is a headline generated from the source text.

Original source: https://nvd.nist.gov/vuln/detail/CVE-2026-21521

First tracked: February 15, 2026 at 08:51 PM ET, from NVD/CVE Database

Classifier: claude-haiku-5-5, prompt v4

Classifier confidence: 80% (self-assessed)

Topics

Coding assistants

Summary

Mitigation

Topics

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