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Arbitrary File Write via Symlink Validation Bypass in Language Servers for AWS

IdentifiersCVE-2026-12958CWE-59

CVE-2026-12958 is a high-severity arbitrary file write vulnerability in Language Servers for AWS prior to version 1.69.0. The issue is caused by missing validation of symbolic links when processing workspace content. If a local user opens a maliciously crafted workspace containing a symlink that resolves to a path outside the workspace trust boundary, the language server may follow that symlink and write to an unintended file location outside the trusted workspace. The flaw is a trust-boundary violation in symlink handling rather than a remotely exploitable network issue.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can allow modification of files outside the intended workspace directory, violating the workspace trust boundary. Depending on what target path is reachable and writable by the affected user account, this could lead to unauthorized alteration of local configuration or project files, corruption of developer environment state, or other unintended file modifications. The provided content does not establish direct remote code execution from this CVE alone, but arbitrary file write outside the workspace boundary can create follow-on security risk.

Mitigation

If you can’t patch tonight, do this now.

No workaround is available according to the advisory. Until patched, avoid opening or trusting untrusted or suspicious workspaces, repositories, or projects that may contain malicious symbolic links. Where possible, restrict use of affected IDE integrations to trusted codebases only until the language server is updated.

Remediation

Patch, then assume compromise.

Upgrade Language Servers for AWS to version 1.69.0 or later. AWS also recommends upgrading affected Amazon Q Developer IDE plugins to fixed releases that bundle the remediated language server, and patching any forked or derivative code to incorporate the fix.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Amazon Web ServicesLanguage Servers For Awsapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

9 SOURCESView more in app

security weekNews

Jun 26, 2026

Amazon Q Flaw Enabled Cloud Credential Theft via Malicious Repositories - SecurityWeek

A related symbolic link handling issue in Amazon Q Developer/AWS Language Server mentioned alongside CVE-2026-12957.

the hacker newsNews

Jun 26, 2026

Amazon Q Developer Flaw Could Let Malicious Repos Run Code via MCP Configs

A flaw in Language Servers for AWS caused by a missing symlink check that could permit arbitrary file writes outside the workspace trust boundary.

cvefeed high severityNews

Jun 23, 2026

CVE-2026-12958 - Arbitrary file write in Language Servers for AWS

An arbitrary file write vulnerability in Language Servers for AWS caused by missing symlink validation, allowing writes outside the workspace trust boundary when a local user opens a maliciously crafted workspace.

What this page doesn’t show

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-12958

NVD

nvd.nist.gov/vuln/detail/CVE-2026-12958

MITRE CWE · CWE-59

cwe.mitre.org