HighCVE-2026-63443

    Coder: Workspace agent API insecure redirect handling allowed cross-agent file read and write (CVE-2026-63443)

    Published Last modified Sources: OSV, CVE.org

    What is affected, what to do

    Coder allows organizations to provision remote development environments via Terraform. Prior to 2.29.19, 2.32.9, 2.33.10, and 2.34.4, agentConn.apiClient() follows redirects while its custom transport accepts the host from the redirected request URL when the port is the workspace agent HTTP API port 4. An authenticated user who controls a modified workspace agent and knows another online agent's UUID can derive the victim's tailnet address and redirect control-plane requests to that agent.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Affected
    • Coder gte 2.27.0, < 2.29.19..*

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.3

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: Vendor (CNA), CVSS v3

    8.3

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: OSV, CVE.org

    0.8 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 55.2

    Show all metrics
    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    93.16 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.3 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.3
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.8 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    55.2
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 15 September 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-863, CWE-918

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Coder allows organizations to provision remote development environments via Terraform. Prior to 2.29.19, 2.32.9, 2.33.10, and 2.34.4, agentConn.apiClient() follows redirects while its custom transport accepts the host from the redirected request URL when the port is the workspace agent HTTP API port 4. An authenticated user who controls a modified workspace agent and knows another online agent's UUID can derive the victim's tailnet address and redirect control-plane requests to that agent. HTTP 301, 302, and 303 redirects can redirect read requests, while HTTP 307 and 308 preserve replayable write and process-start requests. The redirected workspace agent file APIs can read or write files as the victim workspace user, and affected versions exposing the workspace agent process API can execute commands after a redirected file write, crossing workspace and tenant boundaries. This issue is fixed in versions 2.29.19, 2.32.9, 2.33.10, and 2.34.4.

    Source: OSV (Open Source Vulnerabilities), NVD (NIST), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    codercoder
    • ≥ 2.27.0, < 2.29.19
    • —
    gogithub.com/coder/coder
    • —
    • —
    gogithub.com/coder/coder/v2
    • 2.33.0
    • 2.34.0
    • 2.27.0
    • 2.30.0
    • —
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-863Incorrect Authorization

      Class

      The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

      Entry at MITRE CWE-863

    • CWE-918Server-Side Request Forgery (SSRF)

      Base

      The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

      Entry at MITRE CWE-918

    References & sources

    • github.comcoder/coder/security/advisories/GHSA-qrwj-vh9x-gw5vx_refsource_CONFIRM
    • github.comcoder/coder/pull/26600x_refsource_MISC
    • github.comcoder/coder/pull/26611x_refsource_MISC
    • github.comcoder/coder/pull/26612x_refsource_MISC
    • github.comcoder/coder/pull/26613x_refsource_MISC
    • github.comcoder/coder/pull/26622x_refsource_MISC
    • github.comcoder/coder/commit/2312b67bc52c4e314c18c4b4be5dcf5500c94ad7x_refsource_MISC
    • github.comcoder/coder/commit/812549d671d0f5a0b45adcee860d37b70aaddccdx_refsource_MISC
    • github.comcoder/coder/commit/ec3ba84c0002f47dd979c073cde1ab345acbaea5x_refsource_MISC
    • github.comcoder/coder/commit/eeb2624549ddb85538e493af3e678fdb185a809fx_refsource_MISC
    • github.comcoder/coder/commit/f8bdec5add4711650d5bfb6ff93d0cc9d7821c81x_refsource_MISC
    • github.comcoder/coder/releases/tag/v2.29.19x_refsource_MISC
    • github.comcoder/coder/releases/tag/v2.32.9x_refsource_MISC
    • github.comcoder/coder/releases/tag/v2.33.10x_refsource_MISC
    • github.comcoder/coder/releases/tag/v2.34.4x_refsource_MISC
    • github.comcoder/coderpackage

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-63443","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-15T17:31:25.407398Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    2. ReceivedGitHub

      CVSS V3.1: AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L

      Weakness type: CWE-918, CWE-863

      Description added or changed

      Show 20 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      Coder allows organizations to provision remote development environments via Terraform. Prior to 2.29.19, 2.32.9, 2.33.10, and 2.34.4, agentConn.apiClient() follows redirects while its custom transport accepts the host from the redirected request URL when the port is the workspace agent HTTP API port 4. An authenticated user who controls a modified workspace agent and knows another online agent's UUID can derive the victim's tailnet address and redirect control-plane requests to that agent. HTTP 301, 302, and 303 redirects can redirect read requests, while HTTP 307 and 308 preserve replayable write and process-start requests. The redirected workspace agent file APIs can read or write files as the victim workspace user, and affected versions exposing the workspace agent process API can execute commands after a redirected file write, crossing workspace and tenant boundaries. This issue is fixed in versions 2.29.19, 2.32.9, 2.33.10, and 2.34.4.
      CVSSadded
      —
      AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
      Weakness type (CWE)added
      —
      CWE-918
      Weakness type (CWE)added
      —
      CWE-863
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/63xxx/CVE-2026-63443.json">CVE-2026-63443</a>
      Referenceadded
      —
      https://github.com/coder/coder/commit/2312b67bc52c4e314c18c4b4be5dcf5500c94ad7
      Referenceadded
      —
      https://github.com/coder/coder/commit/812549d671d0f5a0b45adcee860d37b70aaddccd
      Referenceadded
      —
      https://github.com/coder/coder/commit/ec3ba84c0002f47dd979c073cde1ab345acbaea5
      Referenceadded
      —
      https://github.com/coder/coder/commit/eeb2624549ddb85538e493af3e678fdb185a809f
      Referenceadded
      —
      https://github.com/coder/coder/commit/f8bdec5add4711650d5bfb6ff93d0cc9d7821c81
      Referenceadded
      —
      https://github.com/coder/coder/pull/26600
      Referenceadded
      —
      https://github.com/coder/coder/pull/26611
      Referenceadded
      —
      https://github.com/coder/coder/pull/26612
      Referenceadded
      —
      https://github.com/coder/coder/pull/26613
      Referenceadded
      —
      https://github.com/coder/coder/pull/26622
      Referenceadded
      —
      https://github.com/coder/coder/releases/tag/v2.29.19
      Referenceadded
      —
      https://github.com/coder/coder/releases/tag/v2.32.9
      Referenceadded
      —
      https://github.com/coder/coder/releases/tag/v2.33.10
      Referenceadded
      —
      https://github.com/coder/coder/releases/tag/v2.34.4
      Referenceadded
      —
      https://github.com/coder/coder/security/advisories/GHSA-qrwj-vh9x-gw5v

      Source identifier: security-advisories@github.com

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